Materials Computation & Modeling

2022

PhysRevL

Raman Linewidth Contributions from Four-Phonon and Electron-Phonon Interactions in Graphene

Han, Zherui, Yang, Xiaolong, Sullivan, Sean E., Feng, Tianli, Shi, Li, Li, Wu, and Ruan, Xiulin

Phys. Rev. Lett. Jan 2022

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2021

Phys. Rev. B
Tuning the phonon transport in bilayer graphene to an anomalous regime dominated by electron-phonon scattering

Yang, X., Liu, Z., Meng, F., and Li, W.

Physical Review B 2021

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Recent studies have revealed the significance of electron-phonon interaction (EPI) in phonon transport at intermediate temperatures. In some metals, the EPI can even dominate over the anharmonic phonon-phonon (ph-ph) scattering, leading to an anomalous phonon transport regime in which the lattice thermal conductivity becomes nearly temperature () independent in contrast to the usual dependence. However, the experimental verification of this anomalous transport regime is very challenging due to the difficulty in separating the phonon contributions from the dominating electron ones to the measured total thermal conductivity in metals. In this work, using first-principles calculations, we predict that in bilayer graphene, the phonon transport can be driven to the anomalous regime by tuning the doping level. At high doping levels close to the Van Hove singularity, the EPI can result in a fivefold reduction of at room temperature, and becomes independent. This anomalous behavior is found to have its origin in three aspects: (i) mirror symmetry breaking enables direct coupling between flexural phonons, the dominant carriers of , and electrons; (ii) dominance of normal processes in the anharmonic ph-ph scattering facilitates the EPI to be more prominent; (iii) dominance of these normal ph-ph processes induces the indirect effect of EPI on . This is distinct from monolayer graphene, where the mirror symmetry prohibits the direct scattering of the flexural phonons by electrons and only the indirect EPI affects . This work gives insight into the manipulation of heat conduction via externally induced EPI in two-dimensional materials in which mirror symmetry breaks and normal processes dominate the ph-ph scattering. ©2021 American Physical Society
@article{Yang2021, author = {Yang, X. and Liu, Z. and Meng, F. and Li, W.}, title = {Tuning the phonon transport in bilayer graphene to an anomalous regime dominated by electron-phonon scattering}, journal = {Physical Review B}, year = {2021}, volume = {104}, number = {10}, doi = {10.1103/PhysRevB.104.L100306}, art_number = {L100306}, note = {cited By 0}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85116429337&doi=10.1103%2fPhysRevB.104.L100306&partnerID=40&md5=90377ef1a7d41165956ca712a18588f6}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; College of Physics, Center of Quantum Materials and Devices, Chongqing University, Chongqing, 401331, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
J Phys Condens Matter
Revisiting the thermal conductivity of Si, Ge and diamond from first principles: Roles of atomic mass and interatomic potential

Guo, G., Yang, X., Carrete, J., and Li, W.

Journal of Physics Condensed Matter 2021

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The thermal conductivity (κ) of nonmetals is determined by the constituent atoms, the crystal structure and interatomic potentials. Although the group-IV elemental solids Si, Ge and diamond have been studied extensively, a detailed understanding of the connection between the fundamental features of their energy landscapes and their thermal transport properties is still lacking. Here, starting from first principles, we analyze those factors, including the atomic mass (m) and the second- (harmonic) and third-order (anharmonic) interatomic force constants (IFCs). Both the second- and third-order IFCs of Si and Ge are very similar, and thus Si and Ge represent ideal systems to understand how the atomic mass alone affects κ. Although the group velocity (v) decreases with increasing atomic mass (v-1), the phonon lifetime (τ) follows the opposite trend (m). Since the contribution to κ from each phonon mode is approximately proportional v 2 τ, κ is lower for the heavier element, namely Ge. Although the extremely high thermal conductivity of diamond is often attributed to weak anharmonic scattering, the anharmonic component of the interatomic potential is not much weaker than those of Si and Ge, which seems to be overlooked in the literature. In fact, the absolute magnitude of the third-order IFCs is much larger in diamond, and the ratios of the third-order IFCs with respect to the second-order ones are comparable to those of Si and Ge. We also explain the experimentally measured κ of high-quality diamonds (Inyushikin et al 2018 Phys. Rev. B 97 144305) by introducing boundary scattering into the picture, and obtain good agreement between calculations and measurements. © 2021 IOP Publishing Ltd.
@article{Guo2021, author = {Guo, G. and Yang, X. and Carrete, J. and Li, W.}, title = {Revisiting the thermal conductivity of Si, Ge and diamond from first principles: Roles of atomic mass and interatomic potential}, journal = {Journal of Physics Condensed Matter}, year = {2021}, volume = {33}, number = {28}, doi = {10.1088/1361-648X/abfd4e}, art_number = {285702}, note = {cited By 0}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85107390646&doi=10.1088%2f1361-648X%2fabfd4e&partnerID=40&md5=f83e5f20a0289f0cbc55540137f8b9b6}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Institute of Materials Chemistry, TU Wien, Vienna, A-1060, Austria}, publisher = {IOP Publishing Ltd}, issn = {09538984}, coden = {JCOME}, pubmed_id = {33930883}, abbrev_source_title = {J Phys Condens Matter}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Mat. Today Phy.
Indirect electron-phonon interaction leading to significant reduction of thermal conductivity in graphene

Yang, X., Jena, A., Meng, F., Wen, S., Ma, J., Li, X., and Li, W.

Materials Today Physics 2021

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We investigate the effect of electron-phonon interaction (EPI) on the lattice thermal conductivity κph of graphene from first-principles calculations. By employing an iterative solution of Boltzmann transport equation (BTE), we highlight the marked effect of the indirect coupling between the flexural acoustic (ZA) phonons and electrons on the thermal conductivity in graphene. Although the ZA phonons, the dominant carriers of κph, do not interact with electrons directly due to the reflection symmetry with respect to the basal plane, their anharmonic interactions with the in-plane transverse acoustic (TA) and longitudinal acoustic (LA) phonons that can be effectively scattered by electrons have a significant effect on κph. This is originated from the dominance of normal processes over Umklapp processes in graphene. Specifically, this indirect effect can result in up to 21% reduction of κph even at room temperature, and 32% reduction in κph at 200 K. Moreover, κph does not decrease monotonically with increasing charge carrier density n. Instead, κph is minimized at ∼ 4.9×1014cm−2. This unusual finding is found to be strongly correlated with the electron density of states at corresponding Fermi levels. This indirect effect should also exist widely in other materials, whose intrinsic lattice thermal conductivities are dominated by normal processes. On the other hand, we also explore the electronic thermal conductivity κe varying with n. Intriguingly, at room temperature κe starts increasing dramatically at n=4.9×1014cm−2, where the corresponding Bloch-Grüneisen transition temperature ΘBG exceeds the room temperature. © 2020 Elsevier Ltd
@article{Yang2022, author = {Yang, X. and Jena, A. and Meng, F. and Wen, S. and Ma, J. and Li, X. and Li, W.}, title = {Indirect electron-phonon interaction leading to significant reduction of thermal conductivity in graphene}, journal = {Materials Today Physics}, year = {2021}, volume = {18}, doi = {10.1016/j.mtphys.2020.100315}, art_number = {100315}, note = {cited By 2}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097782088&doi=10.1016%2fj.mtphys.2020.100315&partnerID=40&md5=fcde808d6bc9f42446e31588ac665037}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States; School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China}, publisher = {Elsevier Ltd}, issn = {25425293}, abbrev_source_title = {Mat. Today Phy.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys Rev Lett
Ultrahigh Thermal Conductivity of θ -Phase Tantalum Nitride

Kundu, A., Yang, X., Ma, J., Feng, T., Carrete, J., Ruan, X., Madsen, G.K.H., and Li, W.

Physical Review Letters 2021

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Extracting long-lasting performance from electronic devices and improving their reliability through effective heat management requires good thermal conductors. Taking both three- and four-phonon scattering as well as electron-phonon and isotope scattering into account, we predict that semimetallic θ-phase tantalum nitride (θ-TaN) has an ultrahigh thermal conductivity (κ), of 995 and 820 W m-1 K-1 at room temperature along the a and c axes, respectively. Phonons are found to be the main heat carriers, and the high κ hinges on a particular combination of factors: weak electron-phonon scattering, low isotopic mass disorder, and a large frequency gap between acoustic and optical phonon modes that, together with acoustic bunching, impedes three-phonon processes. On the other hand, four-phonon scattering is found to be significant. This study provides new insight into heat conduction in semimetallic solids and extends the search for high-κ materials into the realms of semimetals and noncubic crystal structures. © 2021 American Physical Society.
@article{Kundu2021, author = {Kundu, A. and Yang, X. and Ma, J. and Feng, T. and Carrete, J. and Ruan, X. and Madsen, G.K.H. and Li, W.}, title = {Ultrahigh Thermal Conductivity of θ -Phase Tantalum Nitride}, journal = {Physical Review Letters}, year = {2021}, volume = {126}, number = {11}, doi = {10.1103/PhysRevLett.126.115901}, art_number = {115901}, note = {cited By 7}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103130434&doi=10.1103%2fPhysRevLett.126.115901&partnerID=40&md5=55f0610570b084aec901d998a0b0ad5c}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Institute of Materials Chemistry, TU Wien, Vienna, A-1060, Austria; School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, United States; School of Mechanical Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907-2088, United States}, publisher = {American Physical Society}, issn = {00319007}, coden = {PRLTA}, pubmed_id = {33798386}, abbrev_source_title = {Phys Rev Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true}, selected = {true} }
ACS Appl. Mater. Interfaces
High Thermal Conductivity of Wurtzite Boron Arsenide Predicted by including Four-Phonon Scattering with Machine Learning Potential

Liu, Z., Yang, X., Zhang, B., and Li, W.

ACS Applied Materials and Interfaces 2021

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Materials with high thermal conductivity are of great importance to the thermal management of modern electronic devices. Recently, it was found that cubic boron arsenide (c-BAs) is a high thermal conductivity (κ) material with a value of μ1300 W/(m·K) at room temperature (RT), where four-phonon scattering plays a crucial role in limiting the κ. In this work, with four-phonon scattering included, we find that the κ of wurtzite BAs (w-BAs) reaches as high as 1036 W/(m·K) along the a-b plane at RT, decreasing by 43% compared to the calculation without considering four-phonon scattering. The similar phonon transport properties between c-BAs and w-BAs can be understood in terms of similar projected density of states and scattering rates, which have the origin in crystal structural resemblance. To accelerate the calculation, the moment tensor potential derived from machine learning is adopted and proven to be a reliable and efficient method to obtain high-order interatomic force constants. © 2021 American Chemical Society.
@article{Liu2021, author = {Liu, Z. and Yang, X. and Zhang, B. and Li, W.}, title = {High Thermal Conductivity of Wurtzite Boron Arsenide Predicted by including Four-Phonon Scattering with Machine Learning Potential}, journal = {ACS Applied Materials and Interfaces}, year = {2021}, doi = {10.1021/acsami.1c11595}, note = {cited By 0}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85114407385&doi=10.1021%2facsami.1c11595&partnerID=40&md5=6725f14ac9d34cbf699f2c1f6b562323}, affiliation = {Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; Institute of Microscale Optoelectronics, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China}, publisher = {American Chemical Society}, issn = {19448244}, abbrev_source_title = {ACS Appl. Mater. Interfaces}, document_type = {Review}, source = {Scopus}, bibtex_show = {true} }

2020

Inorg. Chem.
Lattice Thermal Transport in Monolayer Group 13 Monochalcogenides MX (M = Ga, In; X = S, Se, Te): Interplay of Atomic Mass, Harmonicity, and Lone-Pair-Induced Anharmonicity

Nissimagoudar, A.S., Rashid, Z., Ma, J., and Li, W.

Inorganic Chemistry 2020

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We perform a systematic study of the lattice dynamics and the lattice thermal conductivity, κ, of monolayer group 13 monochalcogenides MX (M = Ga, In; X = S, Se, Te) by combining an iterative solution for linearized phonon Boltzmann transport equation and density functional theory. Among the competing factors influencing κ, harmonic parameters along with the atomic masses dominate over anharmonicity. An increase in atomic mass leads to a decrease in phonon frequencies and phonon group velocities and consequently in κ. At T = 300 K, the calculated κ values are 54.9, 48.1, 44.3, 25.0, 22.3, and 17.3 W m-1 K-1 for GaS, InS, GaSe, InSe, GaTe, and InTe monolayers, respectively. Further analysis of anharmonic scattering rates and average scattering matrix elements evidences that the anharmonicity characterized by the third-order IFCs in GaS and InS are the largest among all monolayer group 13 monochalcogenides despite the largest κ values. This is attributed to a strong interaction between nonbonding lone-pair s electrons around the S atom and adjacent bonding electrons. In addition, the κ of these monolayers further reduces to 50% for sample sizes 300-400 nm. Our findings provide fundamental insights into thermal transport in monolayer group 13 monochalcogenides and should stimulate further experimental exploration of thermal transport in these materials for possible theromoelectric and thermal management applications. © 2020 American Chemical Society.
@article{Nissimagoudar202014899, author = {Nissimagoudar, A.S. and Rashid, Z. and Ma, J. and Li, W.}, title = {Lattice Thermal Transport in Monolayer Group 13 Monochalcogenides MX (M = Ga, In; X = S, Se, Te): Interplay of Atomic Mass, Harmonicity, and Lone-Pair-Induced Anharmonicity}, journal = {Inorganic Chemistry}, year = {2020}, volume = {59}, number = {20}, pages = {14899-14909}, doi = {10.1021/acs.inorgchem.0c01407}, note = {cited By 2}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093706098&doi=10.1021%2facs.inorgchem.0c01407&partnerID=40&md5=576e84a2c897852a5ae6d51012d8a803}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Chemical Society}, issn = {00201669}, coden = {INOCA}, pubmed_id = {32993283}, abbrev_source_title = {Inorg. Chem.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
ACS Appl. Mater. Interfaces
Strain-Induced Ultrahigh Electron Mobility and Thermoelectric Figure of Merit in Monolayer α-Te

Ma, J., Meng, F., He, J., Jia, Y., and Li, W.

ACS Applied Materials and Interfaces 2020

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In line with the classic phonon-glass electron-crystal (PGEC) paradigm, semiconducting and semimetallic multinary compounds remain the cornerstone of the state-of-the-art thermoelectric materials. By contrast, elemental PGEC is very rare. In this work, we report a thermoelectric study of monolayer α-Te by first-principles calculations and solving the parameter-free Boltzmann transport equation. It is found that monolayer α-Te possesses high electron mobility (about 2500 cm2 V-1 s-1) at room temperature due to small effective mass, low phonon frequencies, and thus a restricted phase space for electron-phonon scattering. In monolayer α-Te, the electrons near the conduction band edge are mainly scattered by the heavily populated quadratically dispersing out-of-plane acoustic (ZA) phonon modes. The thermoelectric figure of merit (ZT) for n-type monolayer α-Te is 0.55 at 300 K and 1.46 at 700 K. Notably, tensile strain stiffens the ZA modes, yielding a linear energy-momentum dispersion relation and the removal of the diverging thermal population of ZA phonons. Consequently, the electron mobility is enhanced. At a 4% tensile strain, the electron mobility can reach up to 8000 cm2 V-1 s-1 at room temperature while the thermal conductivity is almost unaffected, yielding a state-of-the-art ZT value of 0.94 and 2.03 in n-type monolayer α-Te at 300 and 700 K, respectively. For completeness, the thermoelectric study of p-type monolayer α-Te is also conducted. These results beckon further experiments toward high-performance α-Te-based thermoelectric materials via doping, alloying, and compositing. Copyright © 2020 American Chemical Society.
@article{Ma202043901, author = {Ma, J. and Meng, F. and He, J. and Jia, Y. and Li, W.}, title = {Strain-Induced Ultrahigh Electron Mobility and Thermoelectric Figure of Merit in Monolayer α-Te}, journal = {ACS Applied Materials and Interfaces}, year = {2020}, volume = {12}, number = {39}, pages = {43901-43910}, doi = {10.1021/acsami.0c10236}, note = {cited By 5}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092680953&doi=10.1021%2facsami.0c10236&partnerID=40&md5=60bf4b89576e8bce9c99251f4981bb81}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States; International Laboratory for Quantum Functional Materials of Henan, School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001, China}, publisher = {American Chemical Society}, issn = {19448244}, pubmed_id = {32870654}, abbrev_source_title = {ACS Appl. Mater. Interfaces}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Nanotechnology
Electronic and thermal properties of monolayer beryllium oxide from first principles

Xia, C., Li, W., Ma, D., and Zhang, L.

Nanotechnology 2020

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Monolayer beryllium oxide (BeO), a new graphene-like metal oxide material, has attracted tremendous interest since it was demonstrated to have high dynamic, thermal, kinetic and mechanical stabilities in recent years. This discovery enriches the catalogue of 2D materials and paves the way for the exploration of relevant properties. In this work, the electronic and thermal properties of monolayer BeO are predicted by first-principles calculations. Compared with graphene and monolayer hexagonal boron nitride (h-BN), the monolayer BeO is an insulator and its electrons are highly localized around O and Be atoms (ionic nature). More importantly, the thermal conductivity of monolayer BeO is found to be 266 Wm-1K-1 at 300 K, which is lower than that of graphene and h-BN but higher than most other 2D materials. Further spectrum analysis reveals that 75% of the thermal conductivity of monolayer BeO is contributed by phonons with a frequency from 0 to 5.4 THz. With the characteristics of wide bandgap and high thermal conductivity, monolayer BeO shows great potential for applications in electronic device packages and Li-ion batteries. © 2020 IOP Publishing Ltd.
@article{Xia2020, author = {Xia, C. and Li, W. and Ma, D. and Zhang, L.}, title = {Electronic and thermal properties of monolayer beryllium oxide from first principles}, journal = {Nanotechnology}, year = {2020}, volume = {31}, number = {37}, doi = {10.1088/1361-6528/ab97d0}, art_number = {375705}, note = {cited By 5}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087529325&doi=10.1088%2f1361-6528%2fab97d0&partnerID=40&md5=35533a9cbfde40b30a1135780284f3cb}, affiliation = {NNU-SULI Thermal Energy Research Center (NSTER), Center for Quantum Transport and Thermal Energy Science (CQTES), School of Physics and Technology, Nanjing Normal University, Nanjing, 210023, China; Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China}, publisher = {Institute of Physics Publishing}, issn = {09574484}, coden = {NNOTE}, pubmed_id = {32470952}, abbrev_source_title = {Nanotechnology}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Large lattice thermal conductivity, interplay between phonon-phonon, phonon-electron, and phonon-isotope scatterings, and electrical transport in molybdenum from first principles

Wen, S., Ma, J., Kundu, A., and Li, W.

Physical Review B 2020

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We describe an ab initio phonon Boltzmann transport equation (BTE) approach accounting for phonon-electron scattering in addition to the well-established phonon-phonon and isotope scatterings. The phonon BTE is linearized and can be exactly solved beyond the relaxation time approximation (RTA). We use this approach to study the lattice thermal conductivity (κph) of molybdenum (Mo). κph of Mo is found to possess several anomalous features: (1) like in another group VI element tungsten (W), κph, with a large value of 37 W m-1 K-1 at room temperature, follows weak temperature dependence due to interplay between phonon-phonon (ph-ph), phonon-electron (ph-el), and phonon-isotope (isotope) scatterings; and (2) compared with W, though Mo is much lighter in mass, Mo has a smaller κph. This is attributed to weaker interatomic bonding, larger isotope mixture, and larger density of states at Fermi level in Mo. In isotopically pure samples, κph increases from 37 to 48 W m-1 K-1 at room temperature. Considering the similarity of the phonon dispersion, our work suggests that chromium should also have a large κph, which, rather than the complexity of the electronic band structure argued in the literature, accounts for the significant deviation of measured Lorenz number L from the expected Sommerfeld value. The electrical conductivity (σ) and electronic thermal conductivity (κe) of Mo are also calculated by using an ab initio electron BTE approach. σ and the total thermal conductivity (κ) agree with the experimental data reasonably. These results demonstrate that the ab initio calculations can quantify the lattice and electronic contributions to κ. We also look into the cumulative σ and κph with respect to electron and phonon mean free paths (MFPs), respectively, in order to reveal the size effect in Mo. The MFPs of electrons contributing to conductivity range from 5 to 22 nm, whereas the MFPs of phonons primarily distribute between 5 and 73 nm with more than 80% contribution to κph. This suggests that a reduced Lorenz number can be observed in Mo nanostructures when the relevant size goes below ∼70 nm. © 2020 American Physical Society.
@article{Wen2020, author = {Wen, S. and Ma, J. and Kundu, A. and Li, W.}, title = {Large lattice thermal conductivity, interplay between phonon-phonon, phonon-electron, and phonon-isotope scatterings, and electrical transport in molybdenum from first principles}, journal = {Physical Review B}, year = {2020}, volume = {102}, number = {6}, doi = {10.1103/PhysRevB.102.064303}, art_number = {064303}, note = {cited By 4}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090143536&doi=10.1103%2fPhysRevB.102.064303&partnerID=40&md5=ea7c371bedb30a37cf5acd0c35543ba6}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology, Nanjing Normal University, Nanjing, 210023, China}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Mat. Today Phy.
Anisotropic thermoelectric figure-of-merit in Mg3Sb2

Meng, F., Sun, S., Ma, J., Chronister, C., He, J., and Li, W.

Materials Today Physics 2020

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In view of the tensor nature of thermoelectric (TE) figure of merit ZT, the lack of experimental data on its anisotropic transport properties, and the recent advances in theoretical modeling, here we calculated the TE properties of n-type and p-type Mg3Sb2 as a function of temperature along major crystallographic axes using a parameter-free first principles algorithm of electron–phonon interactions and phonon-phonon interactions limited Boltzmann transport equations for charge carriers and phonons, respectively. The calculated ZT curves of n-type Mg3Sb2 are found to be nearly isotropic, and the highest calculated ZT is about 2.1 at 750 K, in reasonable agreement with the experimental results and thus validating our calculations. In contrast, we found strong anisotropy of ZT in p-type Mg3Sb2, with the highest calculated ZT value attaining 1.5 at 750 K along the c-axis and 0.6 in the ab-plane at 750 K, respectively. The strong anisotropy in p-type ZT is mainly dominated by the electrical conductivity along different directions which relies on the anisotropic charge carrier effective mass. In light of the fact that the experimentally measured ZT values are less than unity in polycrystalline p-type Mg3Sb2, these results attest the key role of texture in the performance improvement of polycrystalline p-type Mg3Sb2 so as to mitigate the performance imbalance between the n-type and p-type Mg3Sb2 legs toward higher device performance. © 2020 Elsevier Ltd
@article{Meng2020, author = {Meng, F. and Sun, S. and Ma, J. and Chronister, C. and He, J. and Li, W.}, title = {Anisotropic thermoelectric figure-of-merit in Mg3Sb2}, journal = {Materials Today Physics}, year = {2020}, volume = {13}, doi = {10.1016/j.mtphys.2020.100217}, art_number = {100217}, note = {cited By 14}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084353901&doi=10.1016%2fj.mtphys.2020.100217&partnerID=40&md5=7e67b558577805f9fbeee864dfbbcbdb}, affiliation = {Department of Physics and Astronomy, Clemson University, Clemson, 29634, United States; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China; School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China}, publisher = {Elsevier Ltd}, issn = {25425293}, abbrev_source_title = {Mat. Today Phy.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Mat. Today Phy.
Anomalously large lattice thermal conductivity in metallic tungsten carbide and its origin in the electronic structure

Kundu, A., Ma, J., Carrete, J., Madsen, G.K.H., and Li, W.

Materials Today Physics 2020

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Usually, the thermal conductivity is predominantly contributed by electrons in metals. In this work, by using first-principles calculations we find that in tungsten carbide (WC) the phonon-contributed thermal conductivities (κph) are 131 and 158 Wm−1K−1 along the a and c axes, respectively, three times as much as the electronic contribution (κe). In isotopically pure samples, κph can be further increased to 204 and 249 Wm−1K−1 along the a and c axes, respectively, which is comparable to the κe of Al. The anomalously large κph is attributed to the weak phonon-phonon and electron-phonon scattering, both of which have their origin in the electronic structure of the group-VI carbides. The Fermi energy falls within the pseudogap between the bonding and antibonding states, suggesting stronger interatomic bonding and weaker electron-phonon scattering than in group-IV and V carbides. The unique combination of strong interatomic bonding and large atomic mass of W results in a large acoustic-optical gap in the phonon dispersion, suppressing phonon-phonon scattering. In contrast, in another group-VI carbide, MoC, also with strong interatomic bonding, the smaller atomic mass of Mo increases the acoustic phonon frequencies and reduces the acoustic-optical gap. Furthermore, electron-phonon scattering, though not very strong in absolute magnitude, also plays an important role in phonon scattering, leading to a weak temperature dependence of κph in WC. The large thermal conductivity, persisting at high temperatures, facilitates the use of this material in applications such as cutting tools. © 2020 Elsevier Ltd
@article{Kundu2020, author = {Kundu, A. and Ma, J. and Carrete, J. and Madsen, G.K.H. and Li, W.}, title = {Anomalously large lattice thermal conductivity in metallic tungsten carbide and its origin in the electronic structure}, journal = {Materials Today Physics}, year = {2020}, volume = {13}, doi = {10.1016/j.mtphys.2020.100214}, art_number = {100214}, note = {cited By 9}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083445830&doi=10.1016%2fj.mtphys.2020.100214&partnerID=40&md5=03ac4edba9635348ddfdb052b340a468}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Institute of Materials Chemistry, TU Wien, Vienna, A-1060, Austria; School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China}, publisher = {Elsevier Ltd}, issn = {25425293}, abbrev_source_title = {Mat. Today Phy.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Physica Status Solidi Rapid Res. Lett.
High Thermoelectric Figure of Merit of Full-Heusler Ba2AuX (X = As, Sb, and Bi)

Ma, J., Nissimagoudar, A.S., Wang, S., and Li, W.

Physica Status Solidi - Rapid Research Letters 2020

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Herein, an unprecedentedly high thermoelectric figure of merit (ZT) in full-Heusler compounds of Ba2AuX (X = As, Sb, and Bi) is predicted by performing first-principles calculations combined with parameter-free Boltzmann transport equations. It is found that the ZT can reach up to 5 and 3 at 800 K in n- and p-type systems, respectively, and can be as high as 1.7 and 1.0 at room temperature. The high ZT is attributed to the high power factor coupled with low thermal conductivity. The spin–orbit coupling (SOC) is necessarily considered because the exclusion of SOC significantly overestimates the electron mobility but underestimates the hole mobility of Ba2AuBi. The Lorenz number is found to exhibit an expected monotonical increase with carrier concentration, in contrast to the reported literature results. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
@article{Ma2020, author = {Ma, J. and Nissimagoudar, A.S. and Wang, S. and Li, W.}, title = {High Thermoelectric Figure of Merit of Full-Heusler Ba2AuX (X = As, Sb, and Bi)}, journal = {Physica Status Solidi - Rapid Research Letters}, year = {2020}, volume = {14}, number = {6}, doi = {10.1002/pssr.202000084}, art_number = {2000084}, note = {cited By 4}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082743565&doi=10.1002%2fpssr.202000084&partnerID=40&md5=7ae0089662cea26780c904770822c7e1}, affiliation = {School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; School of Physical Science and Technology, Inner Mongolia University, Hohhot, 010021, China}, publisher = {Wiley-VCH Verlag}, issn = {18626254}, abbrev_source_title = {Physica Status Solidi Rapid Res. Lett.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
J. Mater. Chem. A
Combined treatment of phonon scattering by electrons and point defects explains the thermal conductivity reduction in highly-doped Si

Dongre, B., Carrete, J., Wen, S., Ma, J., Li, W., Mingo, N., and Madsen, G.K.H.

Journal of Materials Chemistry A 2020

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The mechanisms causing the reduction in lattice thermal conductivity in highly P- A nd B-doped Si are looked into in detail. Scattering rates of phonons by point defects, as well as by electrons, are calculated from first principles. Lattice thermal conductivities are calculated considering these scattering mechanisms both individually and together. It is found that at low carrier concentrations and temperatures phonon scattering by electrons is dominant and can reproduce the experimental thermal conductivity reduction. However, at higher doping concentrations the scattering rates of phonons by point defects dominate the ones by electrons except for the lowest phonon frequencies. Consequently, phonon scattering by point defects contributes substantially to the thermal conductivity reduction in Si at defect concentrations above 1019 cm-3 even at room temperature. Only when, phonon scattering by both point defects and electrons are taken into account, excellent agreement is obtained with the experimental values at all temperatures. © 2019 The Royal Society of Chemistry.
@article{Dongre20201273, author = {Dongre, B. and Carrete, J. and Wen, S. and Ma, J. and Li, W. and Mingo, N. and Madsen, G.K.H.}, title = {Combined treatment of phonon scattering by electrons and point defects explains the thermal conductivity reduction in highly-doped Si}, journal = {Journal of Materials Chemistry A}, year = {2020}, volume = {8}, number = {3}, pages = {1273-1278}, doi = {10.1039/c9ta11424f}, note = {cited By 11}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078705736&doi=10.1039%2fc9ta11424f&partnerID=40&md5=fda8cd18d2ac42ad288226702f23e8b2}, affiliation = {Institute of Materials Chemistry, TU Wien, Vienna, A-1060, Austria; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; LITEN, CEA-Grenoble, 17 rue des Martyrs, Grenoble Cedex 9, 38054, France}, publisher = {Royal Society of Chemistry}, issn = {20507488}, coden = {JMCAE}, abbrev_source_title = {J. Mater. Chem. A}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Chem. Chem. Phys.
Quantifying the rigidity of 2D carbides (MXenes)

Hu, T., Yang, J., Li, W., Wang, X., and Li, C.M.

Physical Chemistry Chemical Physics 2020

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MXenes represent a family of surface-functionalized two-dimensional (2D) carbides and nitrides with potential applications in the field of flexible electronics, which rely on their elasticity and flexibility. However, the knowledge on such aspects is rather limited. Here, taking the four most typical MXenes, namely, Ti2CTx, Ti3C2Tx, Nb2CTx and Nb4C3Tx (T = O, OH and F) as examples, we evaluate their intrinsic in-plane stiffness and out-of-plane rigidity at the nanoscale with respect to their functional groups, chemical components and thickness by first-principles calculations. We find that both the in-plane stiffness (C) and out-of-plane bending rigidity (D) of MXenes are highly dependent on the thickness of MX and the surface functional groups. Specifically, the thickness and surface functionalization increase C and D significantly. The Foppl-von Karman numbers per area (C/D), as the flexibility descriptor, of MXenes are comparable with that of the MoS2 monolayer, indicating MXenes as a class of strong yet bendable materials. The effective thickness, the critical parameter bridging C and D, of MXenes is determined to be only two-thirds of the average layer spacing. This study provides a fundamental basis for quantifying the rigidity of MXenes at the nanoscale. © 2020 the Owner Societies.
@article{Hu20202115, author = {Hu, T. and Yang, J. and Li, W. and Wang, X. and Li, C.M.}, title = {Quantifying the rigidity of 2D carbides (MXenes)}, journal = {Physical Chemistry Chemical Physics}, year = {2020}, volume = {22}, number = {4}, pages = {2115-2121}, doi = {10.1039/c9cp05412j}, note = {cited By 9}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078686349&doi=10.1039%2fc9cp05412j&partnerID=40&md5=1a996f0d44d211d4a9f77d1c583712ad}, affiliation = {Institute of Materials Science and Devices, Suzhou University of Science and Technology, Suzhou, 215009, China; Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016, China; University of Science and Technology of China, Hefei, 230026, China; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Institute for Cross-field Science, College of Life Science, Qingdao University, Qingdao, 200671, China}, publisher = {Royal Society of Chemistry}, issn = {14639076}, coden = {PPCPF}, pubmed_id = {31904063}, abbrev_source_title = {Phys. Chem. Chem. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2019

npj Computational Mater.
Body-centered-cubic structure and weak anharmonic phonon scattering in tungsten

Chen, Y., Ma, J., Wen, S., and Li, W.

npj Computational Materials 2019

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It was recently found that the anharmonic phonon–phonon scattering in tungsten is extremely weak at high frequencies, leading to a predominance of electron–phonon scattering and consequently anomalous phonon transport behaviors. In this work, we calculate the phonon linewidths of W along high-symmetry directions from first principles. We find that the weak phonon–phonon scattering can be traced back to two factors. The first is the triple degeneracy of the phonon branches at the P and H points, a universal property of elemental body-centered-cubic (bcc) structures. The second is a relatively isotropic character of the phonon dispersions. When both are met, phonon–phonon scattering rates must vanish at the P and H points. The weak phonon–phonon scattering feature is also applicable to Mo and Cr. However, in other elemental bcc substances like Na, the isotropy condition is violated due to the unusually soft character of the lower transverse acoustic phonon branch along the Γ-N direction, opening emission channels and leading to much stronger phonon–phonon scattering. We also look into the distributions of electron mean-free paths (MFPs) at room temperature in tungsten, which can help engineer the resistivity of nanostructured W for applications such as interconnects. © 2019, The Author(s).
@article{Chen2019, author = {Chen, Y. and Ma, J. and Wen, S. and Li, W.}, title = {Body-centered-cubic structure and weak anharmonic phonon scattering in tungsten}, journal = {npj Computational Materials}, year = {2019}, volume = {5}, number = {1}, doi = {10.1038/s41524-019-0235-7}, art_number = {98}, note = {cited By 5}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073675302&doi=10.1038%2fs41524-019-0235-7&partnerID=40&md5=99cd857cb73767e782c78a45b1433f76}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {Nature Publishing Group}, issn = {20573960}, abbrev_source_title = {npj Computational Mater.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Appl Phys Lett
Raman spectra and dimensional effect on the charge density wave transition in GdTe3

Chen, Y., Wang, P., Wu, M., Ma, J., Wen, S., Wu, X., Li, G., Zhao, Y., Wang, K., Zhang, L., Huang, L., Li, W., and Huang, M.

Applied Physics Letters 2019

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The studies of the dimensional effect on the charge density wave (CDW) transition have attracted a lot of attention since the rise of 2D materials. In this paper, we synthesize high-quality single-crystal GdTe3, a member of the layered rare-earth metal tritelluride family with CDW transitions, and systematically study the temperature-dependent Raman spectra of bulk and few-layer GdTe3. Combining with first-principle calculations, the CDW and phonon Raman peaks are distinguished and characterized. We demonstrate that the CDW order can be enhanced in few-layer GdTe3, and the CDW transition temperature increases from 377 K to 431 K as the thickness reduces from the bulk to 10 nm. We speculate that this enhancement of the CDW order in the GdTe3 thin layer is likely due to the chemical pressure release. Our studies demonstrate that the dimensionality provides a valuable tuning parameter for manipulating the CDW properties of GdTe3. © 2019 Author(s).
@article{Chen2020, author = {Chen, Y. and Wang, P. and Wu, M. and Ma, J. and Wen, S. and Wu, X. and Li, G. and Zhao, Y. and Wang, K. and Zhang, L. and Huang, L. and Li, W. and Huang, M.}, title = {Raman spectra and dimensional effect on the charge density wave transition in GdTe3}, journal = {Applied Physics Letters}, year = {2019}, volume = {115}, number = {15}, doi = {10.1063/1.5118870}, art_number = {151905}, note = {cited By 4}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073189690&doi=10.1063%2f1.5118870&partnerID=40&md5=75c5fd342660af7254419c318edf0b35}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China; Shenzhen Key Laboratory of Quantum Science and Engineering, Shenzhen, 518055, China}, publisher = {American Institute of Physics Inc.}, issn = {00036951}, coden = {APPLA}, abbrev_source_title = {Appl Phys Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Physic. Rev. Mat.
Effect of local chemistry and structure on thermal transport in doped GaAs

Kundu, A., Otte, F., Carrete, J., Erhart, P., Li, W., Mingo, N., and Madsen, G.K.H.

Physical Review Materials 2019

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Using a first-principles approach, we analyze the impact of DX centers formed by S, Se, and Te dopant atoms on the thermal conductivity of GaAs. Our results are in good agreement with experiments and unveil the physics behind the drastically different effect of each kind of defect. We establish a causal chain linking the electronic structure of the dopants to the thermal conductivity of the bulk solid, a macroscopic transport coefficient. Specifically, the presence of lone pairs leads to the formation of structurally asymmetric DX centers that cause resonant scattering of incident phonons. The effect of such resonances is magnified when they affect the part of the spectrum most relevant for thermal transport. We show that, in the vibrational spectrum of the perturbed system, they take the form of modes that are localized around the defect but still extended enough to couple with incident phonons. Finally, we illustrate the connection between flat adjacent minima in the energy landscape and resonant phonon scattering through detailed analyses of the energy landscape of the defective structures. © 2019 American Physical Society.
@article{Kundu2019, author = {Kundu, A. and Otte, F. and Carrete, J. and Erhart, P. and Li, W. and Mingo, N. and Madsen, G.K.H.}, title = {Effect of local chemistry and structure on thermal transport in doped GaAs}, journal = {Physical Review Materials}, year = {2019}, volume = {3}, number = {9}, doi = {10.1103/PhysRevMaterials.3.094602}, art_number = {094602}, note = {cited By 4}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072599694&doi=10.1103%2fPhysRevMaterials.3.094602&partnerID=40&md5=f70d41fbfcc8c72c58dc978ddd26ff80}, affiliation = {Institute of Materials Chemistry, TU Wien, Vienna, A-1060, Austria; Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; Chalmers University of Technology, Department of Physics, Gothenburg, Sweden; LITEN, CEA-Grenoble, Grenoble Cedex 9, 38054, France}, publisher = {American Physical Society}, issn = {24759953}, abbrev_source_title = {Physic. Rev. Mat.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Nanoscale Horiz.
Keggin-type polyoxometalate cluster as an active component for redox-based nonvolatile memory

Chen, X., Huang, P., Zhu, X., Zhuang, S., Zhu, H., Fu, J., Nissimagoudar, A.S., Li, W., Zhang, X., Zhou, L., Wang, Y., Lv, Z., Zhou, Y., and Han, S.-T.

Nanoscale Horizons 2019

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Redox-based nonvolatile memory, where the nanoscale redox process is generally conceived to account for resistance change in external electrical stimuli, is attracting much scientific interest because of its high potential for application in next-generation memory and neuromorphic computing systems. However, materials used in current redox-based resistive switching memory are usually restricted by bulk transition metal oxides. Polyoxometalates (POMs) - a class of discrete early transition metal oxide molecular clusters - are gaining popularity in emerging applications of molecular electronic devices owing to their nanoscale size, high stability, and rich reversible redox potential. This paper reports nonvolatile memory associated with the redox behavior of POMs. Resistive switching mechanisms of POM-based resistive switching memory were systematically investigated for the first time. The intrinsic redox property of POMs was confirmed to initiate the formation of conductive filaments, which are developed by the migration of oxygen ions, as verified through electron energy loss spectroscopy. The results of this study could provide valuable insight into application of redox molecular-based memory for high-density data storage. © The Royal Society of Chemistry.
@article{Chen2019697, author = {Chen, X. and Huang, P. and Zhu, X. and Zhuang, S. and Zhu, H. and Fu, J. and Nissimagoudar, A.S. and Li, W. and Zhang, X. and Zhou, L. and Wang, Y. and Lv, Z. and Zhou, Y. and Han, S.-T.}, title = {Keggin-type polyoxometalate cluster as an active component for redox-based nonvolatile memory}, journal = {Nanoscale Horizons}, year = {2019}, volume = {4}, number = {3}, pages = {697-704}, doi = {10.1039/c8nh00366a}, note = {cited By 17}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065747164&doi=10.1039%2fc8nh00366a&partnerID=40&md5=f058a37760a22545d7abc896fb1a8b9e}, affiliation = {Shenzhen Key Laboratory of Flexible Memory Materials and Devices, College of Electronic Science and Technology, Shenzhen University, Shenzhen, 518060, China; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China}, publisher = {Royal Society of Chemistry}, issn = {20556756}, abbrev_source_title = {Nanoscale Horiz.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Adv. Electron. Mater.
2D Single-Layer π-Conjugated Nickel Bis(dithiolene) Complex: A Good-Electron-Poor-Phonon Thermoelectric Material

Deng, T., Yong, X., Shi, W., Gan, C.K., Li, W., Hippalgaonkar, K., Zheng, J.-C., Wang, X., Yang, S.-W., Wang, J.-S., and Wu, G.

Advanced Electronic Materials 2019

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Recently, the 2D d 8 planar π-conjugated transition metal complexes have gained extensive attention owing to their extra-high electrical conductivity. Meanwhile, low lattice thermal conductivities can be expected for their soft and microporous structures, suggesting very promising thermoelectric applications. Herein, based on first-principles calculations and molecular dynamics simulations, it is identified that monolayered 2D nickel bis(dithiolene) complex, (NiC 4 S 4 ) n , is indeed such a material that exhibits exceptionally high electron mobility, low lattice thermal conductivity, and thereby excellent thermoelectric performance. The calculated figure of merit at 300 K can reach up to 0.92 for a perfect nanosheet. At the same time, the mechanism behind is uncovered, that is, the weak electron-acoustic-phonon coupling allowing high electron mobility, and its microporous structure decreasing the thermal transport. The surprisingly weak electron-acoustic-phonon coupling arises from mixed bonding–antibonding nature of conduction band. The finding opens a new opportunity for these 2D coordination complexes as potential thermoelectric materials. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
@article{Deng2019, author = {Deng, T. and Yong, X. and Shi, W. and Gan, C.K. and Li, W. and Hippalgaonkar, K. and Zheng, J.-C. and Wang, X. and Yang, S.-W. and Wang, J.-S. and Wu, G.}, title = {2D Single-Layer π-Conjugated Nickel Bis(dithiolene) Complex: A Good-Electron-Poor-Phonon Thermoelectric Material}, journal = {Advanced Electronic Materials}, year = {2019}, volume = {5}, number = {4}, doi = {10.1002/aelm.201800892}, art_number = {1800892}, note = {cited By 13}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062366345&doi=10.1002%2faelm.201800892&partnerID=40&md5=90b9574611ccd20d7ea8a6e3f15c2391}, affiliation = {Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 ConnexisSingapore 138632, Singapore; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, #08-03 InnovisSingapore 138634, Singapore; Department of Physics and the Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Xiamen University, Xiamen, 361005, China; Xiamen University Malaysia, Sepang, Selangor 439000, Malaysia; Department of Physics, Faculty of Science, National University of Singapore, 2 Science Drive 3Singapore 117551, Singapore}, publisher = {Blackwell Publishing Ltd}, issn = {2199160X}, abbrev_source_title = {Adv. Electron. Mater.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Nanoscale
Giant thermal conductivity in diamane and the influence of horizontal reflection symmetry on phonon scattering

Zhu, L., Li, W., and Ding, F.

Nanoscale 2019

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Diamane, a chemically derived two-dimensional material, shows many superior physical and chemical properties similar to diamond thin films. Through the Peierls-Boltzmann transport equation, we reveal giant thermal conductivity in diamane with a stacking order of both AB and AA (respectively, abbreviated as D-AB and D-AA, hereafter) which are both comparable to that of diamond. Like in graphene, the phonon transport falls into the hydrodynamic regime even at room temperature, and the major contribution to the total thermal conductivity comes from the out-of-plane acoustic phonon modes (>40%). In addition, the thermal conductivity shows a dependence on the stacking order, namely, the thermal conductivity of D-AA, ∼2240 W m -1 K -1 at 300 K, is around 15% larger than that of D-AB, which is due to the strong restriction on the phonon scattering phase space induced by the horizontal reflection symmetry in D-AA. Such a kind of restriction, not limited to single atomic plane systems, is a general feature in two-dimensional materials with a horizontal reflection symmetry. © 2019 The Royal Society of Chemistry.
@article{Zhu20194248, author = {Zhu, L. and Li, W. and Ding, F.}, title = {Giant thermal conductivity in diamane and the influence of horizontal reflection symmetry on phonon scattering}, journal = {Nanoscale}, year = {2019}, volume = {11}, number = {10}, pages = {4248-4257}, doi = {10.1039/c8nr08493a}, note = {cited By 24}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062606686&doi=10.1039%2fc8nr08493a&partnerID=40&md5=14fe66a6e52a98028b01c192d5d994a6}, affiliation = {Department of Physics, Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, Jiangsu Key Laboratory of Modern Measurement Technology and Intelligent Systems, Huaiyin Normal University, Huai'an, China; Center for Multidimensional Carbon Materials, Institute for Basic Science UNIST-gil, 50 Ulju-gun, Ulsan, 44919, South Korea; Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; School of Materials Science and Engineering, Ulsan Institute for Science and Technology UNIST-gil, 50 Ulju-gun, Ulsan, 44919, South Korea}, publisher = {Royal Society of Chemistry}, issn = {20403364}, pubmed_id = {30623946}, abbrev_source_title = {Nanoscale}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Phonon-limited carrier mobility and temperature-dependent scattering mechanism of 3C -SiC from first principles

Meng, F., Ma, J., He, J., and Li, W.

Physical Review B 2019

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Electron-phonon coupling is at the core of various regimes of material-based science and technology. Taking 3C-silicon carbide (3C-SiC) as an example, despite its very wide application in high-temperature and high-power devices, the transport properties of 3C-SiC are not yet fully understood at the microscopic level because of inadequate knowledge in electron-phonon coupling. In this paper, with electron-phonon coupling matrix elements calculated from first principles, the phonon limited carrier mobility of 3C-SiC is quantified by solving the Boltzmann transport equation. The calculated mobilities for both holes and electrons are in reasonable agreement with the experimental data. Unlike other polar semiconductors such as GaAs, where the polar-longitudinal-optical (LO)-phonon interactions are the dominant scattering mechanism, the mobilities of electrons and holes are dominated by the intravalley longitudinal acoustic phonon scattering at 300 K due to the low occupation number of high-frequency polar LO phonons in 3C-SiC. The dominant scattering mechanism in 3C-SiC varies with temperature. At high temperature (800 K), LO phonons govern the scattering instead. The maximum mean-free paths of electrons and holes at room temperature are found to be 40 nm and 15 nm, respectively. © 2019 American Physical Society.
@article{Meng2019, author = {Meng, F. and Ma, J. and He, J. and Li, W.}, title = {Phonon-limited carrier mobility and temperature-dependent scattering mechanism of 3C -SiC from first principles}, journal = {Physical Review B}, year = {2019}, volume = {99}, number = {4}, doi = {10.1103/PhysRevB.99.045201}, art_number = {045201}, note = {cited By 18}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060915562&doi=10.1103%2fPhysRevB.99.045201&partnerID=40&md5=4d389d119dc0bca7ca42f2e8ddd45943}, affiliation = {Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology, Nanjing Normal University, Nanjing, 210023, China}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Understanding the thermal conductivity and Lorenz number in tungsten from first principles

Chen, Y., Ma, J., and Li, W.

Physical Review B 2019

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Tungsten is known to have a Lorenz number L larger than the Sommerfeld value (L0=π2kB2/3e2=2.445×10-8V2/deg2) by 30%. By performing fully first-principles calculations, we are able to calculate the electrical conductivity (σ) and quantify the electronic (κe) and the lattice (κph) contributions to the thermal conductivity with a high accuracy. We show that the deviation of L is entirely due to κph, and κe/σT agrees with L0 within 5%. At room temperature, κph is 46 W/m-K, one order of magnitude larger than that in other metals even with smaller atomic mass and higher Debye temperature, and likely the largest of all metals. The large κph is ascribed to the surprisingly weak anharmonic phonon scattering. Apart from the not-strong anharmonic interatomic interaction, the weak anharmonic phonon scattering is also facilitated with the large atomic mass, leading to small thermal displacement. The interplay between the phonon-phonon and electron-phonon scatterings leads to weak temperature dependence of κph, and signifies the importance of an accurate solution to the Boltzmann transport equation beyond the conventional relaxation time approximation. Our findings give insights into the phonon transport in metals. © 2019 American Physical Society.
@article{Chen2021, author = {Chen, Y. and Ma, J. and Li, W.}, title = {Understanding the thermal conductivity and Lorenz number in tungsten from first principles}, journal = {Physical Review B}, year = {2019}, volume = {99}, number = {2}, doi = {10.1103/PhysRevB.99.020305}, art_number = {020305}, note = {cited By 21}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060391442&doi=10.1103%2fPhysRevB.99.020305&partnerID=40&md5=6385b8a19191a6e8768325c5fe4d06cc}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems, Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Inorg. Chem.
Prediction and Characterization of NaGaS 2 , A High Thermal Conductivity Mid-Infrared Nonlinear Optical Material for High-Power Laser Frequency Conversion

Hou, D., Nissimagoudar, A.S., Bian, Q., Wu, K., Pan, S., Li, W., and Yang, Z.

Inorganic Chemistry 2019

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Infrared nonlinear optical (IR NLO) crystals are the major materials to widen the output range of solid-state lasers to mid- or far-infrared regions. The IR NLO crystals used in the middle IR region are still inadequate for high-power laser applications because of deleterious thermal effects (lensing and expansion), low laser-induced damage threshold, and two-photon absorption. Herein, the unbiased global minimum search method was used for the first time to search for IR NLO optical materials and ultimately found a new IR NLO material NaGaS 2 . It meets the stringent demands for IR NLO materials pumped by high-power laser with the highest thermal conductivity among common IR NLO materials able to avoid two-photon absorption, a classic nonlinear coefficient, and wide infrared transparency. © 2018 American Chemical Society.
@article{Hou201993, author = {Hou, D. and Nissimagoudar, A.S. and Bian, Q. and Wu, K. and Pan, S. and Li, W. and Yang, Z.}, title = {Prediction and Characterization of NaGaS 2 , A High Thermal Conductivity Mid-Infrared Nonlinear Optical Material for High-Power Laser Frequency Conversion}, journal = {Inorganic Chemistry}, year = {2019}, volume = {58}, number = {1}, pages = {93-98}, doi = {10.1021/acs.inorgchem.8b01174}, note = {cited By 13}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059634452&doi=10.1021%2facs.inorgchem.8b01174&partnerID=40&md5=541bef7c9f04bfadb1f1a67b33863833}, affiliation = {CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang Technical Institute of Physics and Chemistry, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, 40-1 South Beijing Road, Urumqi, 830011, China; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Chemical Society}, issn = {00201669}, coden = {INOCA}, pubmed_id = {29905473}, abbrev_source_title = {Inorg. Chem.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Chem. Chem. Phys.
Phonon transport and thermoelectric properties of semiconducting Bi2Te2X (X = S, Se, Te) monolayers

Rashid, Z., Nissimagoudar, A.S., and Li, W.

Physical Chemistry Chemical Physics 2019

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Confinement or dimensionality reduction is a novel strategy to reduce the lattice thermal conductivity and, consequently, to improve the thermoelectric conversion performance. Bismuth and tellurium based low-dimensional materials have great potential in this regard. The phonon transport and thermoelectric properties of Bi2Te2X (X = S, Se, Te) monolayers are systematically investigated by employing density functional theory and the Boltzmann transport equation. The calculated lattice thermal conductivity of these 2D systems ranges from ∼1.3 W m-1 K-1 (Bi2Te2Se) to ∼1.5 W m-1 K-1 (Bi2Te3) for a 10 μm system size at room temperature and considering spin-orbit coupling in harmonic force constants. This remarkably low lattice thermal conductivity is attributed to small group velocities and enhanced anharmonic phonon scattering rates. A detailed analysis is presented in terms of mode-level phonon group velocities, anharmonic scattering rates and phonon mean free paths. Our results reveal that the thermal transport in these 2D systems is dominated by in-plane transverse acoustic modes. Additionally, the thermal conductivity can be further reduced by decreasing the sample size due to phonon-boundary scattering. The thermoelectric properties including the Seebeck coefficient, power factor and electrical conductivity are calculated using the semi-classical Boltzmann transport equation within the rigid band approximation. The low thermal conductivities coupled with their high carrier mobilities lead to good thermoelectric power factors. With optimal carrier doping, a figure of merit ∼0.6 can be achieved at room temperature, which increases to ∼0.8 at 700 K, thus making them promising candidates for thermoelectric applications. © 2019 the Owner Societies.
@article{Rashid20195679, author = {Rashid, Z. and Nissimagoudar, A.S. and Li, W.}, title = {Phonon transport and thermoelectric properties of semiconducting Bi2Te2X (X = S, Se, Te) monolayers}, journal = {Physical Chemistry Chemical Physics}, year = {2019}, volume = {21}, number = {10}, pages = {5679-5688}, doi = {10.1039/c8cp05793a}, note = {cited By 32}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062620549&doi=10.1039%2fc8cp05793a&partnerID=40&md5=c13e54fa8b055652bf4aa630cb310c5f}, affiliation = {Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems, Ministry of Education Guangdong Province, College of Optoelectronics Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {Royal Society of Chemistry}, issn = {14639076}, coden = {PPCPF}, pubmed_id = {30799478}, abbrev_source_title = {Phys. Chem. Chem. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2018

J. Phys. Chem. C
Screening Surface Structure of MXenes by High-Throughput Computation and Vibrational Spectroscopic Confirmation

Hu, T., Hu, M., Gao, B., Li, W., and Wang, X.

Journal of Physical Chemistry C 2018

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Functionalized MXenes hold promises in a variety of applications in which the dispensable functional groups are mixed. The functionalization is spontaneously realized through competitive adsorption of active species on the MX matrix during the acid etching process of MAX phases. Nevertheless, the knowledge of proportion and distribution of functional groups on MXenes, i.e., surface structures, is still limited. By high-throughput computation screening, ground-state stable structures of four kinds of typical MXenes - Ti2CTx, Ti3C2Tx, Nb2CTx, and Nb4C3Tx (T = O, F, and OH) - with mixed functional group compositions are figured out for the first time. The multicomponent functional group patterns definitely demonstrate an obvious feature of spatial mixing at a given component. However, the heterogeneous structure has a near linear dependence on the functional group components in terms of free energy. Most functionalized MXenes are dynamically stable except for Nb2CF2 and Nb2C(OH)2 due to their competing displacive counterparts. Last but not least, Raman spectra of the four kinds of MXenes confirm the predicted stable surface structures of MXenes. This study provides a clear fundamental basis for understanding the surface structures of MXenes. © 2018 American Chemical Society.
@article{Hu201818501, author = {Hu, T. and Hu, M. and Gao, B. and Li, W. and Wang, X.}, title = {Screening Surface Structure of MXenes by High-Throughput Computation and Vibrational Spectroscopic Confirmation}, journal = {Journal of Physical Chemistry C}, year = {2018}, volume = {122}, number = {32}, pages = {18501-18509}, doi = {10.1021/acs.jpcc.8b04427}, note = {cited By 54}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050721854&doi=10.1021%2facs.jpcc.8b04427&partnerID=40&md5=6359d56d8493965f5e32d53fb3c503a6}, affiliation = {Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016, China; Institute of Materials Science and Devices, Suzhou University of Science and Technology, Suzhou, 215009, China; School of Materials Science and Engineering, University of Science and Technology of China, Shenyang, 110016, China; Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Chemical Society}, issn = {19327447}, abbrev_source_title = {J. Phys. Chem. C}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Intrinsic phonon-limited charge carrier mobilities in thermoelectric SnSe

Ma, J., Chen, Y., and Li, W.

Physical Review B 2018

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Within the past few years, tin selenide (SnSe) has attracted intense interest due to its remarkable thermoelectric potential for both n- and p-type crystals. In this work, the intrinsic phonon-limited electron/hole mobilities of SnSe are investigated using a Boltzmann transport equation based on first-principles calculated electron-phonon interactions. We find that the electrons have much larger mobilities than the holes. At room temperature, the mobilities of electrons along the a, b, and c axes are 325, 801, and 623 cm2/V s, respectively, whereas those of holes are 100, 299, and 291 cm2/V s, respectively. The anisotropy of mobilities is consistent with the reciprocal effective mass at band edges. The mode-specific analysis shows that the highest longitudinal optical phonons, rather than previously assumed acoustic phonons, dominate the scattering processes and consequently the mobilities in SnSe. The roomerature largest mean free paths of electrons and holes in SnSe are about 21 and 13 nm, respectively. © 2018 American Physical Society.
@article{Ma2018, author = {Ma, J. and Chen, Y. and Li, W.}, title = {Intrinsic phonon-limited charge carrier mobilities in thermoelectric SnSe}, journal = {Physical Review B}, year = {2018}, volume = {97}, number = {20}, doi = {10.1103/PhysRevB.97.205207}, art_number = {205207}, note = {cited By 41}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047482011&doi=10.1103%2fPhysRevB.97.205207&partnerID=40&md5=7ec13132647efe6a86795249cb5c131c}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems, Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Effect of confinement on anharmonic phonon scattering and thermal conductivity in pristine silicon nanowires

Rashid, Z., Zhu, L., and Li, W.

Physical Review B 2018

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The effect of confinement on the anharmonic phonon scattering rates and the consequences thereof on the thermal transport properties in ultrathin silicon nanowires with a diameter of 1-4 nm have been characterized using atomistic simulations and the phonon Boltzmann transport equation. The phonon density of states (PDOS) for ultrathin nanowires approaches a constant value in the vicinity of the Γ point and increases with decreasing diameter, which indicates the increasing importance of the low-frequency phonons as heat carriers. The anharmonic phonon scattering becomes dramatically enhanced with decreasing thickness of the nanowires. In the thinnest nanowire, the scattering rates for phonons above 1 THz are one order of magnitude higher than those in the bulk Si. Below 1 THz, the increase in scattering rates is even much more appreciable. Our numerical calculations revealed that the scattering rates for transverse (longitudinal) acoustic modes follow ω (1/ω) dependence at the low-frequency limit, whereas those for the degenerate flexural modes asymptotically approach a constant value. In addition, the group velocities of phonons are reduced compared with bulk Si except for low-frequency phonons (<1-2 THz depending on the thickness of the nanowires). The increased scattering rates combined with reduced group velocities lead to a severely reduced thermal conductivity contribution from the high-frequency phonons. Although the thermal conductivity contributed by those phonons with low frequencies is instead increased mainly due to the increased PDOS, the total thermal conductivity is still reduced compared to that of the bulk. This work reveals an unexplored mechanism to understand the measured ultralow thermal conductivity of silicon nanowires. © 2018 American Physical Society.
@article{Rashid2018, author = {Rashid, Z. and Zhu, L. and Li, W.}, title = {Effect of confinement on anharmonic phonon scattering and thermal conductivity in pristine silicon nanowires}, journal = {Physical Review B}, year = {2018}, volume = {97}, number = {7}, doi = {10.1103/PhysRevB.97.075441}, art_number = {075441}, note = {cited By 5}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85043755285&doi=10.1103%2fPhysRevB.97.075441&partnerID=40&md5=726e9347efd92f0c355eca80a6c376bc}, affiliation = {Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems, Ministry of Education of Guangdong Province, College of Optoelectronics Engineering, Shenzhen University, Shenzhen, 518060, China; School of Physics and Electronic and Electrical Engineering, Jiangsu Key Construction Laboratory of Modern Measurement Technology and Intelligent Systems, Huaiyin Normal University, Huai'an, Jiangsu, 223300, China}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Physic. Rev. Mat.
Optimizing phonon scattering by tuning surface-interdiffusion-driven intermixing to break the random-alloy limit of thermal conductivity

Yang, X., and Li, W.

Physical Review Materials 2018

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We investigate the evolution of the cross-plane thermal conductivity κ of superlattices (SLs) as interfaces change from perfectly abrupt to totally intermixed, by using nonequilibrium molecular dynamics simulations in combination with the spectral heat current calculations. We highlight the role of surface-interdiffusion-driven intermixing by calculating the κ of SLs with changing interface roughness, whose tuning allows for κ values much lower than the "alloy limit" and the abrupt interface limit in same cases. The interplay between alloy and interface scattering in different frequency ranges provides a physical basis to predict a minimum of thermal conductivity. More specifically, we also explore how the interface roughness affects the thermal conductivities for SL materials with a broad span of atomic mass and bond strength. In particular, we find that (i) only when the "spacer" thickness of SLs increases up to a critical value, κ of rough SLs can break the corresponding "alloy limit," since SLs with different "spacer" thickness have different characteristic length of phonon transport, which is influenced by surface-interdiffusion-driven intermixing to different extend. (ii) Whether κ changes monotonically with interface roughness strongly depends on the period length and intrinsic behavior of phonon transport for SL materials. Especially, for the SL with large period length, there exists an optimal interface roughness that can minimize the thermal conductivity. (iii) Surface-interdiffusion-driven intermixing is more effective in achieving a low κ below the alloy limit for SL materials with large mass mismatch than with small one. (iv) It is possible for SL materials with large lattice mismatch (i.e., bond strength) to design an ideally abrupt interface structure with κ much below the alloy limit. These results have clear implications for optimization of thermal transport for heat management and for the development of thermoelectric materials. © 2018 American Physical Society.
@article{Yang2018, author = {Yang, X. and Li, W.}, title = {Optimizing phonon scattering by tuning surface-interdiffusion-driven intermixing to break the random-alloy limit of thermal conductivity}, journal = {Physical Review Materials}, year = {2018}, volume = {2}, number = {1}, doi = {10.1103/PhysRevMaterials.2.015401}, art_number = {015401}, note = {cited By 4}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059554184&doi=10.1103%2fPhysRevMaterials.2.015401&partnerID=40&md5=d338ec048b761e4c94a93035d4df21a3}, affiliation = {Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi'An Jiaotong University, Xi'an, 710049, China; Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China}, publisher = {American Physical Society}, issn = {24759953}, abbrev_source_title = {Physic. Rev. Mat.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
First-principles study of electron and hole mobilities of Si and GaAs

Ma, J., Nissimagoudar, A.S., and Li, W.

Physical Review B 2018

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With first-principles calculated electron-phonon coupling matrix elements, the phonon-limited electron and hole mobilities of Si and GaAs are studied using the Boltzmann transport equation. The calculated mobilities agree well with the experimental measurements. For electrons in GaAs, the calculated mobility is very sensitive to the band structure characterized by the effective mass and the energy gap between Γ and L valleys, which clarifies the discrepancies between recent literature findings [J.-J. Zhou and M. Bernardi, Phys. Rev. B 94, 201201(R) (2016)2469-995010.1103/PhysRevB.94.201201; T.-H. Liu, Phys. Rev. B 95, 075206 (2017)2469-995010.1103/PhysRevB.95.075206]. Unlike electrons in GaAs, where the longitudinal optical phonon dominates the scattering, the other phonon branches have a comparable influence on the mobility of holes in GaAs. In Si and GaAs, the spin-orbit coupling interaction has a significant effect on the valence bands and, further, on the hole mobilities, without which the calculated mobility is underestimated, especially at relatively low temperatures, while it has almost no effect on the electrons. © 2018 American Physical Society.
@article{Ma2019, author = {Ma, J. and Nissimagoudar, A.S. and Li, W.}, title = {First-principles study of electron and hole mobilities of Si and GaAs}, journal = {Physical Review B}, year = {2018}, volume = {97}, number = {4}, doi = {10.1103/PhysRevB.97.045201}, art_number = {045201}, note = {cited By 55}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040375325&doi=10.1103%2fPhysRevB.97.045201&partnerID=40&md5=99f0932fc0c32d105bf2a6e75454d0f8}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems, Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2017

J Phys Condens Matter
Thermal transport in monolayer InSe

Nissimagoudar, A.S., Ma, J., Chen, Y., and Li, W.

Journal of Physics Condensed Matter 2017

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Two-dimensional InSe, a recently synthesized semiconductor having a moderate band gap, has gained attention due to its ultra high mobility and high photo-responsivity. In this work, we calculate the lattice thermal conductivity (κ) of monolayer InSe by solving the phonon Boltzmann transport equation (BTE) with first-principles calculated inter atomic force constants. κ of monolayer InSe is isotropic and found to be around 27.6 W m at room temperature along the in-plane direction. The size dependence of κ shows the size effect can persist up to 20 μm. Further, κ can be reduced to half by tuning the sample size to 300 nm. This low value suggests that κ might be a limiting factor for emerging nanoelectronic applications of monolayer InSe. © 2017 IOP Publishing Ltd.
@article{Nissimagoudar2017, author = {Nissimagoudar, A.S. and Ma, J. and Chen, Y. and Li, W.}, title = {Thermal transport in monolayer InSe}, journal = {Journal of Physics Condensed Matter}, year = {2017}, volume = {29}, number = {33}, doi = {10.1088/1361-648X/aa7b63}, art_number = {335702}, note = {cited By 36}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026390388&doi=10.1088%2f1361-648X%2faa7b63&partnerID=40&md5=0bb253a62d3b53e878ce8f7dcb6aec6f}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China}, publisher = {Institute of Physics Publishing}, issn = {09538984}, coden = {JCOME}, pubmed_id = {28644149}, abbrev_source_title = {J Phys Condens Matter}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
2D Materials
Effect of aging-induced disorder on the quantum transport properties of few-layer WTe2

Liu, W.L., Chen, M.L., Li, X.X., Dubey, S., Xiong, T., Dai, Z.M., Yin, J., Guo, W.L., Ma, J.L., Chen, Y.N., Tan, J., Li, D., Wang, Z.H., Li, W., Bouchiat, V., Sun, D.M., Han, Z., and Zhang, Z.D.

2D Materials 2017

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The emerging physical phenomena found in transition metal dicalcogenides (TMDCs) have triggered vast investigations in recent years. Among them, nanoelectronics in WTe2 devices have attracted particular attentions due to its exotic band structure that leads to exciting phenomena such as the predicted type-II Weyl semimetallic state. However, the thickness dependence of its quantum transport properties in the two-dimensional limit remains under debate. The major missing ingredient in the previous studies is the aging-induced disorder, as atomically thin layers of TMDCs are often known to be metastable in the ambient atmosphere. Here, we show systematic performance of low temperature quantum electronic transport of few-layer WTe2. It is observed that aging-induced localized electronic states explains the low temperature Coulomb gap in transport measurements, leading to the anomalous magnetotransport which appears to be extrinsic. While few-layered WTe2 shows clear metallic tendency in the fresh state, degraded devices first exhibited a re-entrant insulating behavior, and finally entered a fully insulating state. Correspondingly, a crossover from parabolic to linear magnetoresistance, and, upon further aging, leads to the observation of weak anti-localization. Our study reveals for the first time the correlation between the unusual magnetotransport and disorder in few-layered WTe2, which is indispensable in providing guidance on its future device applications. © 2016 IOP Publishing Ltd.
@article{Liu2017, author = {Liu, W.L. and Chen, M.L. and Li, X.X. and Dubey, S. and Xiong, T. and Dai, Z.M. and Yin, J. and Guo, W.L. and Ma, J.L. and Chen, Y.N. and Tan, J. and Li, D. and Wang, Z.H. and Li, W. and Bouchiat, V. and Sun, D.M. and Han, Z. and Zhang, Z.D.}, title = {Effect of aging-induced disorder on the quantum transport properties of few-layer WTe2}, journal = {2D Materials}, year = {2017}, volume = {4}, number = {1}, doi = {10.1088/2053-1583/4/1/011011}, art_number = {011011}, note = {cited By 16}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014505890&doi=10.1088%2f2053-1583%2f4%2f1%2f011011&partnerID=40&md5=0b9bcdfd6382fe6363b65a6fc5910d94}, affiliation = {Shenyang National Laboratory for Materials Science, Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS), 72 Wenhua Road, Shenyang, 110016, China; School of Material Science and Engineering, University of Science and Technology of China, Anhui, 230026, China; University of Grenoble Alpes, CNRS, Institut Néel, Grenoble, F-38000, France; State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China; Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China}, publisher = {IOP Publishing Ltd}, issn = {20531583}, abbrev_source_title = {2D Materials}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2016

2D Materials
Strong anisotropic thermal conductivity of monolayer WTe2

Ma, J., Chen, Y., Han, Z., and Li, W.

2D Materials 2016

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Tungsten ditelluride (WTe2) has attracted increasing attention due to its large magnetoresistance and pressure-induced superconductivity. In this work, we investigate the thermal conductivity (κ) of monolayer WTe2 by performing first-principles calculations, and find strong anisotropic κ with predicted room-temperature values of 9 and 20 W m-1 K-1 along two principal lattice directions, respectively. Such strong anisotropy suggests the importance of orientation when engineering thermal-related applications based on WTe2. The anisotropy of κ is attributed to the in-plane linear acoustic phonon branches, while the out-of-plane quadratic acoustic phonon branch is almost isotropic. The size dependence of κ shows that the size effect can persists up to 10 μm, and the anisotropy decreases with decreasing sample size due to the suppression of low-frequency anisotropic phonons by boundary scattering. ©2016 IOP Publishing Ltd.
@article{Ma2016, author = {Ma, J. and Chen, Y. and Han, Z. and Li, W.}, title = {Strong anisotropic thermal conductivity of monolayer WTe2}, journal = {2D Materials}, year = {2016}, volume = {3}, number = {4}, doi = {10.1088/2053-1583/3/4/045010}, art_number = {045010}, note = {cited By 29}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006131996&doi=10.1088%2f2053-1583%2f3%2f4%2f045010&partnerID=40&md5=d95d86593365fb9698d8ccb5b4980fbf}, affiliation = {Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China; Shenyang National Laboratory for Materials Science, Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS), 72 Wenhua Road, Shenyang, 110016, China; School of Material Science and Engineering, University of Science and Technology of China, Anhui, 230026, China}, publisher = {IOP Publishing Ltd}, issn = {20531583}, abbrev_source_title = {2D Materials}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Mater. Res. Lett.
Physically founded phonon dispersions of few-layer materials and the case of borophene

Carrete, J., Li, W., Lindsay, L., Broido, D.A., Gallego, L.J., and Mingo, N.

Materials Research Letters 2016

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By building physically sound interatomic force constants, we offer evidence of the universal presence of a quadratic phonon branch in all unstrained 2D materials, thus contradicting much of the existing literature. Through a reformulation of the interatomic force constants (IFCs) in terms of internal coordinates, we find that a delicate balance between the IFCs is responsible for this quadraticity. We use this approach to predict the thermal conductivity of Pmmn borophene, which is comparable to that of MoS2, and displays a remarkable in-plane anisotropy. These qualities may enable the efficient heat management of borophene devices in potential nanoelectronic applications. IMPACT STATEMENT The newly found universality of quadratic dispersion will change the way 2D-material phonons are calculated. Predicted results for borophene shall become a fundamental reference for future research on this material. © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
@article{Carrete2016204, author = {Carrete, J. and Li, W. and Lindsay, L. and Broido, D.A. and Gallego, L.J. and Mingo, N.}, title = {Physically founded phonon dispersions of few-layer materials and the case of borophene}, journal = {Materials Research Letters}, year = {2016}, volume = {4}, number = {4}, pages = {204-211}, doi = {10.1080/21663831.2016.1174163}, note = {cited By 145}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981713434&doi=10.1080%2f21663831.2016.1174163&partnerID=40&md5=a7092c5a4ccc46cdd6f7744cff848b73}, affiliation = {CEA, LITEN, 17 Rue des Martyrs, Grenoble, 38054, France; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Department of Physics, Boston College, Chestnut Hill, MA 02467, United States; Departamento de Física de la Materia Condensada, Facultad de Física, Universidad de Santiago de Compostela, Santiago de Compostela, E-15782, Spain}, publisher = {Taylor and Francis Ltd.}, issn = {21663831}, abbrev_source_title = {Mater. Res. Lett.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Phonon transport in silicon nanowires: The reduced group velocity and surface-roughness scattering

Zhu, L., Li, B., and Li, W.

Physical Review B 2016

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Using a linear-scaling Kubo simulation approach, we have quantitatively investigated the effects of confinement and surface roughness on phonon transport in silicon nanowires (SiNWs) as thick as 55 nm in diameter R. The confinement effect leads to significant reduction of phonon group velocity v in SiNWs compared to bulk silicon except at extremely low phonon frequencies f, which very likely persists in SiNWs several hundreds of nanometers thick, suggesting the inapplicability of bulk properties, including anharmonic phonon scattering, to SiNWs. For instance, the velocity can be reduced by more than 30% for phonons with f>4.5 THz in 55-nm-thick nanowires. In rough SiNWs Casimir’s limit, which is valid in confined macroscopic systems, can underestimate the surface scattering by more than one order of magnitude. For a roughness profile with Lorentzian correlation characterized by root-mean-square roughness σ and correlation length Lr, the frequency-dependent phonon diffusivity D follows power-law dependences D Rασ-βLrγ, where α∼2 and β∼1. On average, γ increases from 0 to 0.5 as R/σ increases. The mean free path and the phonon lifetime essentially follow the same power-law dependences. These dependences are in striking contrast to Casimir’s limit, i.e., D∼vR/3, and manifest the dominant role of the change in the number of atoms due to roughness. The thermal conductivity κ can vary by one order of magnitude with varying σ and Lr in SiNWs, and increasing σ and shortening Lr can efficiently lower κ below Casimir’s limit by one order of magnitude. Our work provides different insights to understand the ultralow thermal conductivity of SiNWs reported experimentally and guidance to manipulate κ via surface roughness engineering. © 2016 American Physical Society.
@article{Zhu2016, author = {Zhu, L. and Li, B. and Li, W.}, title = {Phonon transport in silicon nanowires: The reduced group velocity and surface-roughness scattering}, journal = {Physical Review B}, year = {2016}, volume = {94}, number = {11}, doi = {10.1103/PhysRevB.94.115420}, art_number = {115420}, note = {cited By 6}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84990877529&doi=10.1103%2fPhysRevB.94.115420&partnerID=40&md5=64b5257540ad3de132e32a3928da3714}, affiliation = {Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; School of Physics and Electronic and Electrical Engineering, Jiangsu Key Construction Laboratory of Modern Measurement Technology and Intelligent System, Huaiyin Normal University, Huai'an, Jiangsu, 223300, China; Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309, United States}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Intrinsic ultralow lattice thermal conductivity of the unfilled skutterudite FeSb3

Fu, Y., Singh, D.J., Li, W., and Zhang, L.

Physical Review B 2016

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It is generally accepted that unfilled skutterudites process high lattice thermal conductivity κl that can be efficiently reduced upon filling. Here by using first-principles Boltzmann-Peierls transport calculations, we find pure skutterudite of FeSb3 with no filler in fact has an intrinsic ultralow κl smaller than that of CoSb3 by one order of magnitude. The value is even smaller than those of most of the fully filled skutterudites. This finding means that with FeSb3 as a reference, filling does not necessarily lower κl. The ultralow κl of FeSb3 is a consequence of the overall softening of phonon spectrum, especially the lowering in frequency of optical phonon branches associated with the weakly bonded Sb4 rings. They overlap more with heat-carrying acoustic phonons and significantly increase the phase space for three-phonon anharmonic scattering processes. This provides an alternative non-filling-related mechanism for lowering the κl of skutterudites. © 2016 American Physical Society.
@article{Fu2016, author = {Fu, Y. and Singh, D.J. and Li, W. and Zhang, L.}, title = {Intrinsic ultralow lattice thermal conductivity of the unfilled skutterudite FeSb3}, journal = {Physical Review B}, year = {2016}, volume = {94}, number = {7}, doi = {10.1103/PhysRevB.94.075122}, art_number = {075122}, note = {cited By 17}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981164865&doi=10.1103%2fPhysRevB.94.075122&partnerID=40&md5=979c0562d54eebedc499947e76578986}, affiliation = {College of Materials Science and Engineering, Key Laboratory of Automobile Materials of MOE, Jilin University, Changchun, 130012, China; Institute for Advanced Study, Shenzhen University, 3688 Nanhai Avenue, Shenzhen, 518060, China; Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211-7010, United States}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Appl Phys Lett
Ultralow lattice thermal conductivity in topological insulator TlBiSe2

Ding, G., Carrete, J., Li, W., Gao, G.Y., and Yao, K.

Applied Physics Letters 2016

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We present ab-initio calculations of the phonon thermal transport properties of topological insulator TlBiSe2. Our results point to a very low lattice thermal conductivity, comparable or lower than those of some popular good thermoelectric materials. Furthermore, we find a slight thermal anisotropy between the in-plane and cross-plane directions in TlBiSe2, markedly smaller than those of van-der-Waals topological insulators explored so far. These conclusions are confirmed and explained by comprehensive analysis of the phonon spectrum of TlBiSe2. The combination of ultralow lattice thermal conductivity and small anisotropy makes TlBiSe2 a promising candidate for thermoelectric applications. © 2016 Author(s).
@article{Ding2016, author = {Ding, G. and Carrete, J. and Li, W. and Gao, G.Y. and Yao, K.}, title = {Ultralow lattice thermal conductivity in topological insulator TlBiSe2}, journal = {Applied Physics Letters}, year = {2016}, volume = {108}, number = {23}, doi = {10.1063/1.4953588}, art_number = {233902}, note = {cited By 18}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84974660021&doi=10.1063%2f1.4953588&partnerID=40&md5=013a03abe649fece5cb7a76e47fde3d8}, affiliation = {School of Physics, Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China; CEA-Grenoble, 17 Rue des Martyrs, Grenoble, 38054, France; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Institute of Physics Inc.}, issn = {00036951}, coden = {APPLA}, abbrev_source_title = {Appl Phys Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B
Influence of the optical-acoustic phonon hybridization on phonon scattering and thermal conductivity

Li, W., Carrete, J., Madsen, G.K.H., and Mingo, N.

Physical Review B 2016

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We predict a marked effect of optical-acoustic phonon hybridization on phonon scattering and lattice thermal conductivity (κ), and illustrate it in the case of Fe2Ge3. This material presents very low-lying optical phonons with an energy of 1.8 meV at the Brillouin zone center, which show avoided crossings with longitudinal acoustic (LA) phonons, due to optical-acoustic phonon polarization hybridization. Because the optical phonons have nonvanishing scattering rates, even a small amount of hybridization with the optical phonon can increase the scattering rates of LA phonons by much more than one order of magnitude, causing the contribution of these phonons to κ to vanish. At low temperatures, the contributions of all LA phonons are eliminated, and thus the avoided crossing leads to a reduction of thermal conductivity by more than half. The scattering rates are very sensitive to the optical-acoustic phonon hybridization strength, characterized by the gap at the avoided crossing point and varied with the wave-vector direction. Our work presents a different reduction mechanism of κ in systems with optical-acoustic phonon hybridization, which can benefit the search for new thermoelectric materials. © 2016 American Physical Society.
@article{Li2016, author = {Li, W. and Carrete, J. and Madsen, G.K.H. and Mingo, N.}, title = {Influence of the optical-acoustic phonon hybridization on phonon scattering and thermal conductivity}, journal = {Physical Review B}, year = {2016}, volume = {93}, number = {20}, doi = {10.1103/PhysRevB.93.205203}, art_number = {205203}, note = {cited By 29}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84970967347&doi=10.1103%2fPhysRevB.93.205203&partnerID=40&md5=beaddbb93feb3ea2edbb7d3217a3778e}, affiliation = {CEA-Grenoble, 17 Rue des Martyrs, Grenoble, 38000, France; Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen, 518060, China; ICAMS, Ruhr-Universität Bochum, Bochum, 44780, Germany}, publisher = {American Physical Society}, issn = {24699950}, abbrev_source_title = {Phys. Rev. B}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
J Appl Phys
Intrinsic thermal conductivities and size effect of alloys of wurtzite AlN, GaN, and InN from first-principles

Ma, J., Li, W., and Luo, X.

Journal of Applied Physics 2016

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Despite the fact the alloys of wurtzite AlN, GaN, and InN are widely used in electronics, the studies on their thermal conductivities (κ) are inadequate, and the intrinsic limits are still unknown. In this work, the intrinsic κ of alloys and their films are calculated from first-principles within the virtual crystal treatment. The κ of alloys are strongly suppressed even by a small amount of alloying. For instance, with only 1% alloying of Al or In, κ of GaN decreases about 60%. At relatively high alloying, with concentration between 0.2 and 0.8, the κ of alloys are not significantly changed. At room temperature, the minimal a-axis κ are about 18, 22, and 8 W m-1 K-1, while the minimal c-axis κ are about 22, 27, and 10 W m-1 K-1 for AlxGa1-xN, InxGa1-xN, and InxAl1-xN, respectively. The size effect in films can persist up to a few tens of micrometers, and κ can be reduced by half in about 100 nm thick films. © 2016 AIP Publishing LLC.
@article{Ma2017, author = {Ma, J. and Li, W. and Luo, X.}, title = {Intrinsic thermal conductivities and size effect of alloys of wurtzite AlN, GaN, and InN from first-principles}, journal = {Journal of Applied Physics}, year = {2016}, volume = {119}, number = {12}, doi = {10.1063/1.4944809}, art_number = {125702}, note = {cited By 16}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006139469&doi=10.1063%2f1.4944809&partnerID=40&md5=996253d1b748aafa227ad07800e901cb}, affiliation = {State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China}, publisher = {American Institute of Physics Inc.}, issn = {00218979}, coden = {JAPIA}, abbrev_source_title = {J Appl Phys}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Appl Phys Lett
Ballistic thermal transport in monolayer transition-metal dichalcogenides: Role of atomic mass

Ma, J., Li, W., and Luo, X.

Applied Physics Letters 2016

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We investigate the ballistic thermal transport of monolayer transition-metal dichalcogenides (TMDs), which is crucial for the thermal management of their potential applications in nanoelectronics. We find the thermal conductance is mainly affected by the atomic masses of TMDs. As a consequence, the temperature dependences of thermal conductances of different TMDs cross: At low temperatures below ∼50 K, the thermal conductance increases with the atomic mass, while it exhibits the opposite trend at high temperatures. The crossing behavior of temperature dependent thermal conductance is characteristic of the atomic mass effect, and TMDs provide a model system demonstrating that the thermal conductance can be effectively manipulated via the atomic mass by selecting appropriate atom. In addition, we clarify that in any two dimensional system such as monolayer TMDs and graphene, due to quadratic dispersion of the out-of-plane modes, the thermal conductance and specific heat in the low temperature limit are proportional to T’ and T, respectively. Mainly because of much smaller group velocities of in-plane acoustic phonons, the high temperature thermal conductances of monolayer TMDs are much smaller than graphene. However, due to comparable group velocities of out-of-plane acoustic phonons, below 100 K thermal conductances of monolayer TMDs are rather comparable to graphene if taking the same layer thickness for comparison. © 2016 AIP Publishing LLC.
@article{Ma2021, author = {Ma, J. and Li, W. and Luo, X.}, title = {Ballistic thermal transport in monolayer transition-metal dichalcogenides: Role of atomic mass}, journal = {Applied Physics Letters}, year = {2016}, volume = {108}, number = {8}, doi = {10.1063/1.4942451}, art_number = {082102}, note = {cited By 12}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011950290&doi=10.1063%2f1.4942451&partnerID=40&md5=d644f0999cba994744be7dd2055c18fd}, affiliation = {State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; CEA-Grenoble, 17 Rue des Martyrs, Grenoble, 38000, France}, publisher = {American Institute of Physics Inc.}, issn = {00036951}, coden = {APPLA}, abbrev_source_title = {Appl Phys Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2015

Phys. Rev. B Condens. Matter Mater. Phys.
Electrical transport limited by electron-phonon coupling from Boltzmann transport equation: An ab initio study of Si, Al, and MoS2

Li, W.

Physical Review B - Condensed Matter and Materials Physics 2015

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We demonstrate the ab initio electrical transport calculation limited by electron-phonon coupling by using the full solution of the Boltzmann transport equation (BTE), which applies equally to metals and semiconductors. Numerical issues are emphasized in this work. We show that the simple linear interpolation of the electron-phonon coupling matrix elements from a relatively coarse grid to an extremely fine grid can ease the calculational burden, which makes the calculation feasible in practice. For the Brillouin zone (BZ) integration of the transition probabilities involving one δ function, the Gaussian smearing method with a physical choice of locally adaptive broadening parameters is employed. We validate the calculation in the cases of n-type Si and Al. The calculated conductivity and mobility are in good agreement with experiments. In the metal case we also demonstrate that the Gaussian smearing method with locally adaptive broadening parameters works excellently for the BZ integration with double δ functions involved in the Eliashberg spectral function and its transport variant. The simpler implementation is the advantage of the Gaussian smearing method over the tetrahedron method. The accuracy of the relaxation time approximation and the approximation made by Allen [Phys. Rev. B 17, 3725 (1978)PRBMDO0163-182910.1103/PhysRevB.17.3725] has been examined by comparing with the exact solution of BTE. We also apply our method to n-type monolayer MoS2, for which a mobility of 150 cm2 v-1 s-1 is obtained at room temperature. Moreover, the mean free paths are less than 9 nm, indicating that in the presence of grain boundaries the mobilities should not be effectively affected if the grain boundary size is tens of nanometers or larger. The ab initio approach demonstrated in this paper can be directly applied to other materials without the need for any a priori knowledge about the electron-phonon scattering processes, and can be straightforwardly extended to study cases with electron-impurity scattering. © 2015 American Physical Society.
@article{Li2015, author = {Li, W.}, title = {Electrical transport limited by electron-phonon coupling from Boltzmann transport equation: An ab initio study of Si, Al, and MoS2}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2015}, volume = {92}, number = {7}, doi = {10.1103/PhysRevB.92.075405}, art_number = {075405}, note = {cited By 121}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940099937&doi=10.1103%2fPhysRevB.92.075405&partnerID=40&md5=678b444ed33ffa9ec728a636a27909c7}, affiliation = {Scientific Computing and Modelling NV, De Boelelaan 1083, Amsterdam, 1081 HV, Netherlands}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Ultralow lattice thermal conductivity of the fully filled skutterudite YbFe4Sb12 due to the flat avoided-crossing filler modes

Li, W., and Mingo, N.

Physical Review B - Condensed Matter and Materials Physics 2015

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We study the lattice thermal conductivity (κ) of fully filled skutterudites YbFe4Sb12 and BaFe4Sb12 from first principles. The calculated κ of YbFe4Sb12 is ten times lower than that calculated for BaFe4Sb12, and much lower than any values ever reported for other skutterudites. The ultralow κ of YbFe4Sb12 is closely related to the flat Yb-dominated modes appearing in the frequency range from 5 to 7.2 rad/ps. The flat modes significantly increase the three-phonon scattering channels, which is reflected by the unique characteristics of weighted phase space and leads to much stronger anharmonic scattering of intermediate-frequency optical phonons. Although those flat modes are dominated by the Yb atoms, the filler-related anharmonic interaction does not play a role in the increased phonon scattering. This underlines the importance of the hybridization of the filler and the host matrix in those flat modes, which can be guaranteed by the avoided crossing with acoustic phonons. The depressed phonon spectrum mechanism, common to other skutterudites, also plays a role in the ultralow κ. Our work presents a reduction mechanism of κ by the filler in cage-like structures such as skutterudites and clathrates, and demonstrates the nonuniqueness of the reduction mechanism in these materials. © 2015 American Physical Society.
@article{Li2017, author = {Li, W. and Mingo, N.}, title = {Ultralow lattice thermal conductivity of the fully filled skutterudite YbFe4Sb12 due to the flat avoided-crossing filler modes}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2015}, volume = {91}, number = {14}, doi = {10.1103/PhysRevB.91.144304}, art_number = {144304}, note = {cited By 115}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928923334&doi=10.1103%2fPhysRevB.91.144304&partnerID=40&md5=fd3c55f9118e166e31e630feca54323b}, affiliation = {Scientific Computing and Modelling NV, De Boelelaan 1083, Amsterdam, 1081 HV, Netherlands; CEA-Grenoble, 17 Rue des Martyrs, Grenoble, 38000, France}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
ASME Int. Tech. Conf. Exhib. Packag. Integr. Electron. Photonic Microsystems, InterPACK, collocated ASME Int. Conf. Nanochannels, Microchannels, Minichannels
Intrinsic thermal conductivity of wurtzite ALXGA1-XN, INXGA1-XN and INXAL1-XN from first-principles calculation

Ma, J., Huang, B., Li, W., and Luo, X.

2015

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The thermal conductivities of the alloys of wurtzite AlN, GaN and InN are usually analyzed with the virtual crystal mod- el based on the values of the constituent compounds. However, latest experiments and calculations reveal that the thermal con- ductivity of wurtzite InN is about three times larger than the pre- viously used value. Thus it is necessary to reanalyze the thermal conductivities of these alloys. In this work, the intrinsic ther- mal conductivities of AlxGa1-xN, InxGa1-xN and InxAl1-xN are calculated with first-principles calculations along with the vir- Tual crystal treatment. It is found that the thermal conductiv- ities of these alloys are strongly suppressed even after a small amount of alloying. For instance, the in-plane and out-of-plane thermal conductivities of In0:99Ga0:01N are 66 Wm-1K-1 and 76 Wm-1K-1 respectively, while they are 40 Wm-1K-1 and 48 Wm-1K-1 for In0:99Al0:01N, compared with the corresponding values of 130 Wm-1K-1 and 145 Wm-1K-1 for bulk wurtzite InN. When the fraction x varies from 0.2 to 0.8, the thermal con- ductivities of the alloys do not change much. Additionally, the distribution of mean free path indicates that the size effect can persist up to 10 mm for both pure compounds and their alloys at room temperature. © Copyright 2015 by ASME.
@conference{Ma2015, author = {Ma, J. and Huang, B. and Li, W. and Luo, X.}, title = {Intrinsic thermal conductivity of wurtzite ALXGA1-XN, INXGA1-XN and INXAL1-XN from first-principles calculation}, journal = {ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems, InterPACK 2015, collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels}, year = {2015}, volume = {2}, doi = {10.1115/IPACK2015-48032}, note = {cited By 1}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953924090&doi=10.1115%2fIPACK2015-48032&partnerID=40&md5=6637cf5491dc9a9758c78a3e232cae45}, affiliation = {School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China; Department of Mechanical Engineering, Hong Kong University of Science and Technology, Hong Kong; Scientific Computing and Modelling NV, De Boelelaan 1083, Amsterdam, 1081HV, Netherlands}, publisher = {American Society of Mechanical Engineers}, isbn = {9780791856895}, abbrev_source_title = {ASME Int. Tech. Conf. Exhib. Packag. Integr. Electron. Photonic Microsystems, InterPACK, collocated ASME Int. Conf. Nanochannels, Microchannels, Minichannels}, document_type = {Conference Paper}, source = {Scopus}, bibtex_show = {true} }

2014

Phys. Rev. B Condens. Matter Mater. Phys.
Effect of nitrogen and vacancy defects on the thermal conductivity of diamond: An ab initio Green’s function approach

Katcho, N.A., Carrete, J., Li, W., and Mingo, N.

Physical Review B - Condensed Matter and Materials Physics 2014

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We show that impurities and vacancies affect the thermal conductivity much more strongly than what is predicted by widely accepted models. When local distortions around point defects are strong, standard perturbative approaches fail, and phonon scattering can only be accounted for by an exact Green’s function calculation. We apply the theory to the study, from first-principles, of nitrogen and vacancy defects in diamond. The thermal conductivity is computed by solving the linearized Boltzmann transport equation. The Born approximation underestimates the phonon scattering cross sections of nitrogen and vacancies by factors of 3 and 10, respectively. Thermal conductivity calculations are in good agreement with experiment. © 2014 American Physical Society.
@article{Katcho2014, author = {Katcho, N.A. and Carrete, J. and Li, W. and Mingo, N.}, title = {Effect of nitrogen and vacancy defects on the thermal conductivity of diamond: An ab initio Green's function approach}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2014}, volume = {90}, number = {9}, doi = {10.1103/PhysRevB.90.094117}, art_number = {094117}, note = {cited By 64}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907457054&doi=10.1103%2fPhysRevB.90.094117&partnerID=40&md5=34897a1fd6265e56bb64c22540cdecad}, affiliation = {CIC EnergiGUNE, Albert Einstein 48, Miñano, Álava, 01510, Spain; LITEN, CEA-Grenoble, 17 rue des Martyrs, Grenoble Cedex 9, 38054, France; Scientific Computing and Modelling NV, De Boeleaan 1083, HV Amsterdam, 1081, Netherlands}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Lattice dynamics and thermal conductivity of skutterudites CoSb3 and IrSb3 from first principles: Why IrSb3 is a better thermal conductor than CoSb3

Li, W., and Mingo, N.

Physical Review B - Condensed Matter and Materials Physics 2014

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Materials with heavier atomic masses usually possess lower lattice thermal conductivity (κ). The reported κ of IrSb3 skutterudite is about 35% higher than that of CoSb3, despite Ir being much heavier than Co. We study the lattice dynamics and κ of CoSb3 and IrSb3 from first principles. We unveil the physical reasons for the difference in κ by comparing all the influential factors: phonon velocities, anharmonicity characterized by the third-order interatomic force constants, the weighted phase space W, and the atomic mass. We find the increased mass from Co to Ir is ultimately the dominant factor resulting in the increase of κ in IrSb3, and the other factors tend to reduce κ. Larger mass leads to smaller thermal displacements causing weaker anharmonic scattering. Our work provides deeper insight to understand the correlation of κ of systems sharing the same crystal structure. We also find that the decreases in acoustic phonon frequencies and Debye temperature in IrSb3 are almost entirely due to the mass increase from Co to Ir. © 2014 American Physical Society.
@article{Li2014, author = {Li, W. and Mingo, N.}, title = {Lattice dynamics and thermal conductivity of skutterudites CoSb3 and IrSb3 from first principles: Why IrSb3 is a better thermal conductor than CoSb3}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2014}, volume = {90}, number = {9}, doi = {10.1103/PhysRevB.90.094302}, art_number = {094302}, note = {cited By 43}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84985024352&doi=10.1103%2fPhysRevB.90.094302&partnerID=40&md5=344d90cdae620acfc5ce5df969f2a4ca}, affiliation = {Scientific Computing and Modelling NV, De Boelelaan 1083, Amsterdam, 1081 HV, Netherlands; CEA-Grenoble, 17 Rue des Martyrs, Grenoble, 38000, France}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Appl Phys Lett
Intrinsic thermal conductivity and its anisotropy of wurtzite InN

Ma, J., Li, W., and Luo, X.

Applied Physics Letters 2014

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Despite wurtzite InN being a widely used semiconductor, its intrinsic thermal conductivity (κ) is still little known. In this work, the κ of wurtzite InN is studied from first principles. The calculated room temperature κ is 130 Wm-1K-1 and 145 Wm -1K-1 for the in-plane and out-of-plane direction, respectively, showing an anisotropy of about 11%. The anisotropy increases with decreasing temperature, and it reaches 20% at 100 K. The evident anisotropy is contrast to the conventionally used isotropic assumption, and is explained by performing comprehensive velocity analysis. We also calculate the cumulative κ as a function of mean free path, which can help understand the size dependence of κ in the non-bulk forms. The obtained cumulative κ is in good agreement with the experimental κ of InN films with thicknesses between 0.5 and 2.1 μm, and shows the size effect can persist up to 10 μm thickness at room temperature. © 2014 AIP Publishing LLC.
@article{Ma2014, author = {Ma, J. and Li, W. and Luo, X.}, title = {Intrinsic thermal conductivity and its anisotropy of wurtzite InN}, journal = {Applied Physics Letters}, year = {2014}, volume = {105}, number = {8}, doi = {10.1063/1.4893882}, art_number = {082103}, note = {cited By 27}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907362598&doi=10.1063%2f1.4893882&partnerID=40&md5=019aa8b2beeba3a5d8048c99459b03bc}, affiliation = {State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; Scientific Computing and Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam, Netherlands}, publisher = {American Institute of Physics Inc.}, issn = {00036951}, coden = {APPLA}, abbrev_source_title = {Appl Phys Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Examining the Callaway model for lattice thermal conductivity

Ma, J., Li, W., and Luo, X.

Physical Review B - Condensed Matter and Materials Physics 2014

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The Callaway model [J. Callaway, Phys. Rev. 113, 1046 (1959)PHRVAO0031- 899X10.1103/PhysRev.113.1046], regarded as an improvement over the relaxation time approximation (RTA) for the phonon Boltzmann transport equation (BTE), is widely used in studying lattice thermal conductivity (κ). However, its accuracy needs to be systematically examined. By solving BTE accurately using an iterative method along with the first principles calculation of phonon scatterings, we conduct such an examination of the Callaway model as well as a modified version proposed by Allen [Phys. Rev. B 88, 144302 (2013)PRBMDO1098- 012110.1103/PhysRevB.88.144302] for Si, diamond, and wurtzite AlN. At room temperature, the RTA underestimates κ by 5%, 32%, 11%, and 12% for Si, diamond, and in-plane and cross-plane AlN, respectively. The deviation of the original Callaway model from the accurate κ is -1%, 25%, 1%, and -12%, respectively, while the deviation of Allen’s modified model is 7%, 44%, 13%, and -8%, respectively. The room temperature anisotropy of AlN is 5%, and the anisotropy predicted by RTA, the Callaway model, and Allen’s modified version is 7%, 19%, and 29%, respectively. We conclude that neither the original Callaway model nor Allen’s modified version can generally guarantee an improvement over RTA. In these three systems, we also find that the relaxation times for umklapp processes scale as 1/ω3 at low frequencies for both transverse acoustic (TA) and longitudinal acoustic (LA) modes, and those for normal processes scale as 1/ω and 1/ω2 for TA and LA modes, respectively. © 2014 American Physical Society.
@article{Ma2022, author = {Ma, J. and Li, W. and Luo, X.}, title = {Examining the Callaway model for lattice thermal conductivity}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2014}, volume = {90}, number = {3}, doi = {10.1103/PhysRevB.90.035203}, art_number = {035203}, note = {cited By 55}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904652720&doi=10.1103%2fPhysRevB.90.035203&partnerID=40&md5=bd5aaa1f855217605cec14779ee78fed}, affiliation = {School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; Scientific Computing and Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam, Netherlands}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Thermal conductivity of fully filled skutterudites: Role of the filler

Li, W., and Mingo, N.

Physical Review B - Condensed Matter and Materials Physics 2014

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Using ab initio calculations we have investigated the lattice thermal conductivity (I) of CoSb3 and BaCo4Sb12. The calculated room temperature I of these compounds are 11.5 and 6.1 W/m K, respectively. The change in I upon filling is mainly due to the reduction of phonon lifetimes limited by the anharmonic scattering, which occurs in the whole phonon spectrum, ruling out the postulated â€œrattlingâ€ model. We show that the harmonic interaction instead of the anharmonic interaction between the filler and the host matrix, depressing the phonon spectrum, is at the origin of the reduction of Î upon filling. We believe that the filler plays the same role in other fully filled skutterudites. © 2014 American Physical Society.
@article{Li2018, author = {Li, W. and Mingo, N.}, title = {Thermal conductivity of fully filled skutterudites: Role of the filler}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2014}, volume = {89}, number = {18}, doi = {10.1103/PhysRevB.89.184304}, art_number = {184304}, note = {cited By 110}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902121615&doi=10.1103%2fPhysRevB.89.184304&partnerID=40&md5=3b93d98224cf24989d61246db1a8c943}, affiliation = {CEA-Grenoble, 17 Rue des Martyrs, Grenoble 38000, France}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Phonon thermal transport in strained and unstrained graphene from first principles

Lindsay, L., Li, W., Carrete, J., Mingo, N., Broido, D.A., and Reinecke, T.L.

Physical Review B - Condensed Matter and Materials Physics 2014

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A rigorous first principles Boltzmann-Peierls equation (BPE) for phonon transport approach is employed to examine the lattice thermal conductivity, κL, of strained and unstrained graphene. First principles calculations show that the out-of-plane, flexural acoustic phonons provide the dominant contribution to κL of graphene for all strains, temperatures, and system sizes considered, supporting a previous prediction that used an optimized Tersoff empirical interatomic potential. For the range of finite system sizes considered, we show that the κL of graphene is relatively insensitive to strain. This provides validation for use of the BPE approach to calculate κL for unstrained graphene, which has recently been called into question. The temperature and system size dependence of the calculated κL of graphene is in good agreement with experimental data. The enhancement of κL with isotopic purification is found to be relatively small due to strong anharmonic phonon-phonon scattering. This work provides insight into the nature of phonon thermal transport in graphene, and it demonstrates the power of first principles thermal transport techniques. © 2014 American Physical Society.
@article{Lindsay2014, author = {Lindsay, L. and Li, W. and Carrete, J. and Mingo, N. and Broido, D.A. and Reinecke, T.L.}, title = {Phonon thermal transport in strained and unstrained graphene from first principles}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2014}, volume = {89}, number = {15}, doi = {10.1103/PhysRevB.89.155426}, art_number = {155426}, note = {cited By 249}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899748902&doi=10.1103%2fPhysRevB.89.155426&partnerID=40&md5=bf3384e139bd7ad1861977cddfaa43b1}, affiliation = {NRC Research Associate at Naval Research Laboratory, Washington, DC 20375, United States; Department of Physics, Boston College, Chestnut Hill, MA 02467, United States; LITEN, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France; Naval Research Laboratory, Washington, DC 20375, United States}, publisher = {American Physical Society}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Top. Appl. Phys.
Ab initio thermal transport

Mingo, N., Stewart, D.A., Broido, D.A., Lindsay, L., and Li, W.

Topics in Applied Physics 2014

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Ab initio (or first principles) approaches are able to predict materials properties without the use of any adjustable parameters. This chapter presents some of our recently developed techniques for the ab initio evaluation of the lattice thermal conductivity of crystalline bulk materials and alloys, and nanoscale materials including embedded nanoparticle composites. © Springer Science+Business Media New York 2014.
@article{Mingo2014137, author = {Mingo, N. and Stewart, D.A. and Broido, D.A. and Lindsay, L. and Li, W.}, title = {Ab initio thermal transport}, journal = {Topics in Applied Physics}, year = {2014}, volume = {128}, pages = {137-173}, doi = {10.1007/978-1-4614-8651-0_5}, note = {cited By 0}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928604416&doi=10.1007%2f978-1-4614-8651-0_5&partnerID=40&md5=3715b55e4244411a71769fd70eea452d}, affiliation = {CEA-Grenoble, 17 rue des Martyrs, Grenoble, 38054, France; Cornell Nanoscale Facility, Cornell University, 250 Duffield Hall, Ithaca, NY 14853, United States; Department of Physic, Boston College, 335 Higgins Hall, 140 Commonwealth Ave, Chestnut HillMA 02467, United States; Naval Research Laboratory, Washington, DC 20375, United States}, publisher = {Springer Verlag}, issn = {03034216}, abbrev_source_title = {Top. Appl. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Top. Appl. Phys.
Ab initio thermal transport

Mingo, N., Stewart, D.A., Broido, D.A., Lindsay, L., and Li, W.

Topics in Applied Physics 2014

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Ab initio (or first principles) approaches are able to predict materials properties without the use of any adjustable parameters. This chapter presents some of our recently developed techniques for the ab initio evaluation of the lattice thermal conductivity of crystalline bulk materials and alloys, and nanoscale materials including embedded nanoparticle composites. © Springer Science+Business Media New York 2014.
@article{Mingo2014138, author = {Mingo, N. and Stewart, D.A. and Broido, D.A. and Lindsay, L. and Li, W.}, title = {Ab initio thermal transport}, journal = {Topics in Applied Physics}, year = {2014}, volume = {128}, pages = {137-173}, doi = {10.1007/978-1-4614-8651-0__5}, note = {cited By 39}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927561251&doi=10.1007%2f978-1-4614-8651-0__5&partnerID=40&md5=9eb1f339d304a6d0945215a003d493d0}, affiliation = {CEA-Grenoble, 17 rue des Martyrs, Grenoble, 38054, France; Cornell University, 250 Duffield Hall, Ithaca, NY 14853, United States; Department of Physics, Boston College, 335 Higgins Hall, 140 Commonwealth Ave, Chestnut Hill, MA 02467, United States; Naval Research Laboratory, Washington, DC 20375, United States}, publisher = {Springer Verlag}, issn = {03034216}, abbrev_source_title = {Top. Appl. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Comput Phys Commun
ShengBTE: A solver of the Boltzmann transport equation for phonons

Li, W., Carrete, J., Katcho, N.A., and Mingo, N.

Computer Physics Communications 2014

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ShengBTE is a software package for computing the lattice thermal conductivity of crystalline bulk materials and nanowires with diffusive boundary conditions. It is based on a full iterative solution to the Boltzmann transport equation. Its main inputs are sets of second- and third-order interatomic force constants, which can be calculated using third-party ab-initio packages. Dirac delta distributions arising from conservation of energy are approximated by Gaussian functions. A locally adaptive algorithm is used to determine each process-specific broadening parameter, which renders the method fully parameter free. The code is free software, written in Fortran and parallelized using MPI. A complementary Python script to help compute third-order interatomic force constants from a minimum number of ab-initio calculations, using a real-space finite-difference approach, is also publicly available for download. Here we discuss the design and implementation of both pieces of software and present results for three example systems: Si, InAs and lonsdaleite. Program summary Program title: ShengBTE Catalogue identifier: AESL-v1-0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AESL-v1-0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 292 052 No. of bytes in distributed program, including test data, etc.: 1 989 781 Distribution format: tar.gz Programming language: Fortran 90, MPI. Computer: Non-specific. Operating system: Unix/Linux. Has the code been vectorized or parallelized?: Yes, parallelized using MPI. RAM: Up to several GB Classification: 7.9. External routines: LAPACK, MPI, spglib (http://spglib.sourceforge.net/) Nature of problem: Calculation of thermal conductivity and related quantities, determination of scattering rates for allowed three-phonon processes Solution method: Iterative solution, locally adaptive Gaussian broadening Running time: Up to several hours on several tens of processors. © 2014 Elsevier B.V. All rights reserved.
@article{Li20141747, author = {Li, W. and Carrete, J. and Katcho, N.A. and Mingo, N.}, title = {ShengBTE: A solver of the Boltzmann transport equation for phonons}, journal = {Computer Physics Communications}, year = {2014}, volume = {185}, number = {6}, pages = {1747-1758}, doi = {10.1016/j.cpc.2014.02.015}, note = {cited By 1082}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901233974&doi=10.1016%2fj.cpc.2014.02.015&partnerID=40&md5=5f725579e2bb88b37a44710cbc4fd099}, affiliation = {CEA, DRT, 38054 Grenoble, France}, publisher = {Elsevier}, issn = {00104655}, coden = {CPHCB}, abbrev_source_title = {Comput Phys Commun}, document_type = {Article}, source = {Scopus}, code = {https://bitbucket.org/sousaw/shengbte/}, website = {https://www.shengbte.org/}, bibtex_show = {true}, selected = {true} }
Phys. Rev. X
Finding unprecedentedly low-thermal-conductivity half-heusler semiconductors via high-throughput materials modeling

Carrete, J., Li, W., Mingo, N., Wang, S., and Curtarolo, S.

Physical Review X 2014

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The lattice thermal conductivity (κω) is a key property for many potential applications of compounds. Discovery of materials with very low or high κω remains an experimental challenge due to high costs and time-consuming synthesis procedures. High-throughput computational prescreening is a valuable approach for significantly reducing the set of candidate compounds. In this article, we introduce efficient methods for reliably estimating the bulk κω for a large number of compounds. The algorithms are based on a combination of machine-learning algorithms, physical insights, and automatic ab initio calculations. We scanned approximately 79,000 half-Heusler entries in the AFLOWLIB.org database. Among the 450 mechanically stable ordered semiconductors identified, we find that κω spans more than 2 orders of magnitude-a much larger range than that previously thought. κω is lowest for compounds whose elements in equivalent positions have large atomic radii. We then perform a thorough screening of thermodynamical stability that allows us to reduce the list to 75 systems.We then provide a quantitative estimate of κω for this selected range of systems. Three semiconductors having κω < 5 Wm-1 K-1 are proposed for further experimental study.
@article{Carrete2014, author = {Carrete, J. and Li, W. and Mingo, N. and Wang, S. and Curtarolo, S.}, title = {Finding unprecedentedly low-thermal-conductivity half-heusler semiconductors via high-throughput materials modeling}, journal = {Physical Review X}, year = {2014}, volume = {4}, number = {1}, doi = {10.1103/PhysRevX.4.011019}, art_number = {011019}, note = {cited By 305}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900325125&doi=10.1103%2fPhysRevX.4.011019&partnerID=40&md5=32f47bcdc08227e6e388feb3fd736b62}, affiliation = {CEA-Grenoble, 17 Rue des Martyrs, Grenoble 38054, France; Center for Materials Genomics, Materials Science, Electrical Engineering, Physics and Chemistry, Duke University, Durham, NC 27708, United States}, publisher = {American Physical Society}, issn = {21603308}, abbrev_source_title = {Phys. Rev. X}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2013

Appl Phys Lett
Thermal conductivity and phonon linewidths of monolayer MoS2 from first principles

Li, W., Carrete, J., and Mingo, N.

Applied Physics Letters 2013

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Using ab initio calculations, we have investigated the phonon linewidths and the thermal conductivity (κ) of monolayer MoS2. κ for a typical sample size of 1 μm is 83 W/m K at room temperature in the completely rough edge limit, suggesting κ is not a limiting factor for the electronic application of monolayer MoS2. κ can be further increased by 30% in 10 μm sized samples. Due to strong anharmonicity, isotope enhancement of room temperature κ is only 10% for 1 μm sized samples. However, linewidths can be significantly reduced, for instance, for Raman active modes A1g and E 2 g 1, in isotopically pure samples. © 2013 AIP Publishing LLC.
@article{Li2013, author = {Li, W. and Carrete, J. and Mingo, N.}, title = {Thermal conductivity and phonon linewidths of monolayer MoS2 from first principles}, journal = {Applied Physics Letters}, year = {2013}, volume = {103}, number = {25}, doi = {10.1063/1.4850995}, art_number = {253103}, note = {cited By 239}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891412722&doi=10.1063%2f1.4850995&partnerID=40&md5=cd7fc1d9a65f012c560dd9364c3d1422}, affiliation = {CEA-Grenoble, 17 Rue des Martyrs, Grenoble 38000, France}, issn = {00036951}, coden = {APPLA}, abbrev_source_title = {Appl Phys Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
J Appl Phys
Thermal conductivity of bulk and nanowire InAs, AlN, and BeO polymorphs from first principles

Li, W., and Mingo, N.

Journal of Applied Physics 2013

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We compute the thermal conductivity of the alternative zincblende (ZB) and wurtzite (WZ) phases of InAs, AlN, and BeO. The bulk thermal conductivity of the ZB phase of BeO is predicted to be even higher than that of its WZ phase (the highest amongst all ceramics used in electronic technology). Our calculations agree well with the available experimental measurements for bulk ZB InAs, WZ AlN, WZ BeO, and WZ and ZB InAs nanowires, and we provide predictions for the remaining cases. The predicted good thermal conductor ZB BeO might have interesting applications in improved heat sinks for high performance semiconductor electronics. © 2013 AIP Publishing LLC.
@article{Li2019, author = {Li, W. and Mingo, N.}, title = {Thermal conductivity of bulk and nanowire InAs, AlN, and BeO polymorphs from first principles}, journal = {Journal of Applied Physics}, year = {2013}, volume = {114}, number = {18}, doi = {10.1063/1.4827419}, art_number = {183505}, note = {cited By 39}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887865096&doi=10.1063%2f1.4827419&partnerID=40&md5=68c099b5ddfb41879be050c2f6028e8c}, affiliation = {LITEN, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble, France}, issn = {00218979}, coden = {JAPIA}, abbrev_source_title = {J Appl Phys}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys Rev Lett
Role of surface-segregation-driven intermixing on the thermal transport through planar Si/Ge superlattices

Chen, P., Katcho, N.A., Feser, J.P., Li, W., Glaser, M., Schmidt, O.G., Cahill, D.G., Mingo, N., and Rastelli, A.

Physical Review Letters 2013

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It has been highly debated whether the thermal conductivity κ of a disordered SiGe alloy can be lowered by redistributing its constituent species so as to form an ordered superlattice. By ab initio calculations backed by systematic experiments, we show that Ge segregation occurring during epitaxial growth can lead to κ values not only lower than the alloy’s, but also lower than the perfect superlattice values. Thus we theoretically demonstrate that κ does not monotonically decrease as the Si- and Ge-rich regions become more sharply defined. Instead, an intermediate concentration profile is able to lower κ below both the alloy limit (total intermixing) and also the abrupt interface limit (zero intermixing). This unexpected result is attributed to the peculiar behavior of the phonon mean free path in realistic Si/Ge superlattices, which shows a crossover from abrupt-interface- to alloylike values at intermediate phonon frequencies of ∼3 THz. Our calculated κ’s quantitatively agree with the measurements when the realistic, partially intermixed profiles produced by segregation are considered. © 2013 American Physical Society.
@article{Chen2013, author = {Chen, P. and Katcho, N.A. and Feser, J.P. and Li, W. and Glaser, M. and Schmidt, O.G. and Cahill, D.G. and Mingo, N. and Rastelli, A.}, title = {Role of surface-segregation-driven intermixing on the thermal transport through planar Si/Ge superlattices}, journal = {Physical Review Letters}, year = {2013}, volume = {111}, number = {11}, doi = {10.1103/PhysRevLett.111.115901}, art_number = {115901}, note = {cited By 84}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884248743&doi=10.1103%2fPhysRevLett.111.115901&partnerID=40&md5=013be09628954decbbe4237634fd3d2c}, affiliation = {Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany; Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria; LITEN, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France; Department of Materials Science and Engineering, Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States}, issn = {00319007}, coden = {PRLTA}, abbrev_source_title = {Phys Rev Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
J Appl Phys
Alloy enhanced anisotropy in the thermal conductivity of Si xGe1-x nanowires

Li, W., and Mingo, N.

Journal of Applied Physics 2013

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A strong dependence on crystalline orientation with a most conductive 001 growth direction is theoretically predicted for the thermal conductivity (κ) of SixGe1-x nanowires, even above room temperature and above 1 μm thickness. For instance, the room temperature κ of a 100 nm thick Si0.6Ge0.4 nanowire in the 001 direction is 16% higher than in the 111 direction. In contrast, the dependence for Si or Ge nanowires of the same diameter is much weaker at the same temperature, and 111 direction can be the most conductive one at relatively thin nanowires. In the low temperature limit, the anisotropy of κ can reach 87% at any alloy concentration. The anisotropy arises from the phonon focusing effect on the long mean free path phonons. The low frequency phonons focus in the 001 direction, while the intermediate frequency phonons focus in the 111 direction. The relative contribution to κ from the low frequency phonons is largely enhanced by alloying. Moreover, alloying eliminates the anisotropy caused by the intermediate frequency phonons. Our results imply that orientation has to be taken into account when engineering alloyed nanowire devices, such as thermoelectric modules, even if the corresponding bulk material is completely isotropic. © 2013 AIP Publishing LLC.
@article{Li2020, author = {Li, W. and Mingo, N.}, title = {Alloy enhanced anisotropy in the thermal conductivity of Si xGe1-x nanowires}, journal = {Journal of Applied Physics}, year = {2013}, volume = {114}, number = {5}, doi = {10.1063/1.4817523}, art_number = {054307}, note = {cited By 19}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882277234&doi=10.1063%2f1.4817523&partnerID=40&md5=536c8f749715b8c8977e4b8d332d688b}, affiliation = {CEA-Grenoble, 17 Rue des Martyrs, Grenoble 38000, France}, issn = {00218979}, coden = {JAPIA}, abbrev_source_title = {J Appl Phys}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2012

Phys. Rev. B Condens. Matter Mater. Phys.
Thermal conductivity of bulk and nanowire Mg2Si xSn1-x alloys from first principles

Li, W., Lindsay, L., Broido, D.A., Stewart, D.A., and Mingo, N.

Physical Review B - Condensed Matter and Materials Physics 2012

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The lattice thermal conductivity (κ) of the thermoelectric materials, Mg2Si, Mg2Sn, and their alloys, are calculated for bulk and nanowires, without adjustable parameters. We find good agreement with bulk experimental results. For large nanowire diameters, size effects are stronger for the alloy than for the pure compounds. For example, in 200 nm diameter nanowires κ is lower than its bulk value by 30%, 20%, and 20% for Mg 2Si0.6Sn0.4, Mg2Si, and Mg 2Sn, respectively. For nanowires less than 20 nm thick, the relative decrease surpasses 50%, and it becomes larger in the pure compounds than in the alloy. At room temperature, κ of Mg2SixSn 1-x is less sensitive to nanostructuring size effects than Si xGe1-x, but more sensitive than PbTexSe 1-x. This suggests that further improvement of Mg2Si xSn1-x as a nontoxic thermoelectric may be possible. © 2012 American Physical Society.
@article{Li2012, author = {Li, W. and Lindsay, L. and Broido, D.A. and Stewart, D.A. and Mingo, N.}, title = {Thermal conductivity of bulk and nanowire Mg2Si xSn1-x alloys from first principles}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2012}, volume = {86}, number = {17}, doi = {10.1103/PhysRevB.86.174307}, art_number = {174307}, note = {cited By 369}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870446684&doi=10.1103%2fPhysRevB.86.174307&partnerID=40&md5=935b8627c6595331d2040e016014694e}, affiliation = {LITEN, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France; Naval Research Laboratory, Washington, DC 20375, United States; Department of Physics, Boston College, Chestnut Hill, MA 02467, United States; Cornell Nanoscale Facility, Cornell University, Ithaca, NY 14853, United States}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Appl Phys Lett
Role of phonon anharmonicity in time-domain thermoreflectance measurements

Da Cruz, C.A., Li, W., Katcho, N.A., and Mingo, N.

Applied Physics Letters 2012

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Using ab-initio calculations, we argue that the apparent frequency dependence of the thermal conductivity measured by time-domain thermoreflectance (TDTR) is majorly determined by the balance between harmonic (elastic) and anharmonic (inelastic) phonon channels, and not by ballistic phonons. The match between this theory and experiment is closer than that obtained with previous models. Concrete trends in frequency and temperature dependence are predicted. Reinterpreting frequency modulated time-domain thermoreflectance in terms of elastic vs. inelastic channels explains the markedly different behavior between alloys and non-alloys, and the approach can in principle be applied to other nanostructured material systems. © 2012 American Institute of Physics.
@article{DaCruz2012, author = {Da Cruz, C.A. and Li, W. and Katcho, N.A. and Mingo, N.}, title = {Role of phonon anharmonicity in time-domain thermoreflectance measurements}, journal = {Applied Physics Letters}, year = {2012}, volume = {101}, number = {8}, doi = {10.1063/1.4746275}, art_number = {083108}, note = {cited By 11}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865461897&doi=10.1063%2f1.4746275&partnerID=40&md5=e8a409f6f4c376fe0e67823b23fca2dd}, affiliation = {LITEN, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble, France}, issn = {00036951}, coden = {APPLA}, abbrev_source_title = {Appl Phys Lett}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Thermal conductivity of diamond nanowires from first principles

Li, W., Mingo, N., Lindsay, L., Broido, D.A., Stewart, D.A., and Katcho, N.A.

Physical Review B - Condensed Matter and Materials Physics 2012

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Using ab initio calculations we have investigated the thermal conductivity (κ) of diamond nanowires, unveiling unusual features unique to this system. In sharp contrast with Si, κ(T) of diamond nanowires as thick as 400 nm still increase monotonically with temperature up to 300 K, and room-temperature size effects are stronger than for Si. A marked dependence of κ on the crystallographic orientation is predicted, which is apparent even at room temperature. [001] growth direction always possesses the largest κ in diamond nanowires. The predicted features point to a potential use of diamond nanowires for the precise control of thermal flow in nanoscale devices. © 2012 American Physical Society.
@article{Li2021, author = {Li, W. and Mingo, N. and Lindsay, L. and Broido, D.A. and Stewart, D.A. and Katcho, N.A.}, title = {Thermal conductivity of diamond nanowires from first principles}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2012}, volume = {85}, number = {19}, doi = {10.1103/PhysRevB.85.195436}, art_number = {195436}, note = {cited By 239}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861715400&doi=10.1103%2fPhysRevB.85.195436&partnerID=40&md5=379b01b0d6ae45c7e7d2bf7242782461}, affiliation = {CEA-Grenoble, 17 Rue des Martyrs, Grenoble 38000, France; Naval Research Laboratory, Washington, DC 20375, United States; Department of Physics, Boston College, Chestnut Hill, MA 02467, United States; Cornell Nanoscale Facility, Cornell University, Ithaca, NY 14853, United States}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2011

Phys. Rev. B Condens. Matter Mater. Phys.
Effects of domains in phonon conduction through hybrid boron nitride and graphene sheets

Sevinçli, H., Li, W., Mingo, N., Cuniberti, G., and Roche, S.

Physical Review B - Condensed Matter and Materials Physics 2011

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We theoretically investigate the phonon propagation and thermal conductivity κ in hybrid boron nitride and graphene sheets. By using a real-space Kubo-computational transport scheme, large and disordered graphene structures are simulated, introducing disk-shaped domains with varying sizes of 2 to 8 nm and concentrations ranging from 0% to 100%. A strong influence of the domain size and concentration on the transport properties is obtained. The mean free paths are minimized at 50% domain concentration, and stronger suppression of κ is achieved with smaller domains. It is found to decrease by up to 65% at room temperature when the domain size is 2 nm. These results are beyond the scope of any effective medium approximation. © 2011 American Physical Society.
@article{Sevinçli2011, author = {Sevinçli, H. and Li, W. and Mingo, N. and Cuniberti, G. and Roche, S.}, title = {Effects of domains in phonon conduction through hybrid boron nitride and graphene sheets}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2011}, volume = {84}, number = {20}, doi = {10.1103/PhysRevB.84.205444}, art_number = {205444}, note = {cited By 39}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-82755195647&doi=10.1103%2fPhysRevB.84.205444&partnerID=40&md5=7ce8f742126a620e51d01d67026651fd}, affiliation = {Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, DE-01062 Dresden, Germany; Institute of Physics, Chinese Academy of Sciences, CN-100190 Beijing, China; LITEN, CEA, 17 rue des Martyrs, FR-38042 Grenoble, France; Division of IT Convergence Engineering, POSTECH, Pohang KR-790-784, South Korea; CIN2 (ICN-CSIC), Universitat Autónoma de Barcelona, Campus UAB, ES-08193 Bellaterra (Barcelona), Spain; ICREA, Institució Catalana de Recerca i Estudis Avancats, ES-08070 Barcelona, Spain}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Efficient linear scaling method for computing the thermal conductivity of disordered materials

Li, W., Sevinçli, H., Roche, S., and Cuniberti, G.

Physical Review B - Condensed Matter and Materials Physics 2011

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An efficient order-N real-space Kubo approach is developed for the calculation of the thermal conductivity of complex disordered materials. The method, which is based on the Chebyshev polynomial expansion of the time evolution operator and the Lanczos tridiagonalization scheme, efficiently treats the propagation of phonon wave packets in real space and the phonon diffusion coefficients. The mean free paths and the thermal conductance can be determined from the diffusion coefficients. These quantities can be extracted simultaneously for all frequencies, which is another advantage in comparison with approaches based on the Green’s function. Additionally, multiple scattering phenomena can be followed through the time dependence of the diffusion coefficient deep into the diffusive regime, and the onset of weak or strong phonon localization could possibly be revealed at low temperatures for thermal insulators. The accuracy of our computational scheme is demonstrated by comparing the calculated phonon mean free paths in isotope-disordered carbon nanotubes with Landauer simulations and analytical results. Then the upscalability of the method is illustrated by exploring the phonon mean free paths and the thermal conductance features of edge-disordered graphene nanoribbons having widths of 20 nm and lengths as long as a micrometer, which are beyond the reach of other numerical techniques. It is shown that the phonon mean free paths of armchair nanoribbons are smaller than those of zigzag nanoribbons for the frequency range which dominates the thermal conductance at low temperatures. This computational strategy is applicable to higher-dimensional systems as well as to a wide range of materials. © 2011 American Physical Society.
@article{Li2011, author = {Li, W. and Sevinçli, H. and Roche, S. and Cuniberti, G.}, title = {Efficient linear scaling method for computing the thermal conductivity of disordered materials}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2011}, volume = {83}, number = {15}, doi = {10.1103/PhysRevB.83.155416}, art_number = {155416}, note = {cited By 19}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961058541&doi=10.1103%2fPhysRevB.83.155416&partnerID=40&md5=682a9056e7e373630be603287005069e}, affiliation = {Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, D-01062 Dresden, Germany; CIN2 (ICN-CSIC), Universitat Autónoma de Barcelona, Campus UAB, 08193 Bellaterra (Barcelona), Spain; ICREA, Institució Catalana de Recerca i Estudis Avancats, 08070 Barcelona, Spain; Division of IT Convergence Engineering, National Center for Nanomaterials Technology, POSTECH, Pohang 790-784, South Korea}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }

2010

Phys. Rev. B Condens. Matter Mater. Phys.
Phonon transport in large scale carbon-based disordered materials: Implementation of an efficient order-N and real-space Kubo methodology

Li, W., Sevinçli, H., Cuniberti, G., and Roche, S.

Physical Review B - Condensed Matter and Materials Physics 2010

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We have developed an efficient order- N real-space Kubo approach for the calculation of the phonon conductivity which outperforms state-of-the-art alternative implementations based on the Green’s function formalism. The method treats efficiently the time-dependent propagation of phonon wave packets in real space, and this dynamics is related to the calculation of the thermal conductance. Without loss of generality, we validate the accuracy of the method by comparing the calculated phonon mean free paths in disordered carbon nanotubes (isotope impurities) with other approaches, and further illustrate its upscalability by exploring the thermal conductance features in large width edge-disordered graphene nanoribbons (up to ∼20nm), which is out of the reach of more conventional techniques. We show that edge disorder is the most important scattering mechanism for phonons in graphene nanoribbons with realistic sizes and thermal conductance can be reduced by a factor of ∼10. © 2010 The American Physical Society.
@article{Li2010, author = {Li, W. and Sevinçli, H. and Cuniberti, G. and Roche, S.}, title = {Phonon transport in large scale carbon-based disordered materials: Implementation of an efficient order-N and real-space Kubo methodology}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2010}, volume = {82}, number = {4}, doi = {10.1103/PhysRevB.82.041410}, art_number = {041410}, note = {cited By 47}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956685934&doi=10.1103%2fPhysRevB.82.041410&partnerID=40&md5=333ebc7c7ab202ac736647ac448506ac}, affiliation = {Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, 01062 Dresden, Germany; CIN2, CSIC-ICN, Bellaterra, 08193 Barcelona, Spain; INAC, SP2M, CEA, 17 avenue des Martyrs, 38054 Grenoble, France}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }
Phys. Rev. B Condens. Matter Mater. Phys.
Engineering the figure of merit and thermopower in single-molecule devices connected to semiconducting electrodes

Nozaki, D., Sevinçli, H., Li, W., Gutiérrez, R., and Cuniberti, G.

Physical Review B - Condensed Matter and Materials Physics 2010

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We propose a possible route to achieve high thermoelectric efficiency in molecular junctions by combining a local chemical tuning of the molecular electronic states with the use of semiconducting electrodes. The former allows to control the position of the highest-occupied molecular orbital (HOMO) transmission resonance with respect to the Fermi energy while the latter fulfills a twofold purpose: the suppression of electronlike contributions to the thermopower and the cutoff of the HOMO transmission tails into the semiconductor band gap. As a result a large thermopower can be obtained. Our results strongly suggest that large figures of merit in such molecular junctions can be achieved. © 2010 The American Physical Society.
@article{Nozaki2010, author = {Nozaki, D. and Sevinçli, H. and Li, W. and Gutiérrez, R. and Cuniberti, G.}, title = {Engineering the figure of merit and thermopower in single-molecule devices connected to semiconducting electrodes}, journal = {Physical Review B - Condensed Matter and Materials Physics}, year = {2010}, volume = {81}, number = {23}, doi = {10.1103/PhysRevB.81.235406}, art_number = {235406}, note = {cited By 79}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956337859&doi=10.1103%2fPhysRevB.81.235406&partnerID=40&md5=7be478f64d97a3a57540c8e5f4ac7a7d}, affiliation = {Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, 01062 Dresden, Germany}, issn = {10980121}, coden = {PRBMD}, abbrev_source_title = {Phys. Rev. B Condens. Matter Mater. Phys.}, document_type = {Article}, source = {Scopus}, bibtex_show = {true} }