博士论文答辩：基于第一性原理分析金属与半导体中的电子和声子热输运
日期：2021/05/18 - 2021/05/18
博士论文答辩：基于第一性原理分析金属与半导体中的电子和声子热输运
主讲人：Shouhang Li, Ph.D candidate in University of Michigan – Shanghai Jiao Tong University Joint Institute
时间：2021年5月18日（周二）上午10:00-12:00
地点：Room 403, JI Building
讲座摘要
Thermal conductivity is a fundamental physical parameter that quantifies the heat conduction ability of materials. Both electrons and phonons are involved in the thermal transport of solid materials. Electron-phonon interaction is a basic phenomenon in condensed matter physics. Previous studies based on empirical/semi-empirical models have the drawbacks of unclear physical pictures and weak predictive power. The objectives of this dissertation are to investigate the electron-phonon interaction effects on thermal transport in metals and semiconductors from first-principle calculations.
In the first part of this dissertation, the electron and phonon transport properties of metals are studied. It is proposed that momentum relaxation time should be used for electrical conductivity and energy relaxation time for electronic thermal conductivity. The Lorenz number has significant deviations from the commonly used Sommerfeld value and the Wiedemann-Franz law fails at intermediate/low temperatures. The calculation scheme is further extended to investigate the anomalous thermal transport behaviors in metallic transition-metal nitrides (TMNs) and Dirac semimetal PdTe2. In the second part of this dissertation, the electron-phonon coupling effects on the thermal transport of both doped and intrinsic semiconductors are studied. It is found that SnSe has an ultra-low intrinsic phonon thermal conductivity, which can be further decreased by dopants. However, phonon-electron scattering has little effect on phonon thermal conductivity. Electronic thermal conductivity is usually ignored in intrinsic semiconductors, but it can become important at high temperatures. The first-principles calculation scheme for the electronic thermal conductivity of intrinsic silicon is proposed. It is found that the electronic thermal conductivity contribution to the total thermal conductivity increases with temperature, which is more than 25% at 1500 K. The calculation schemes proposed in the dissertation make it feasible to obtain reliable thermal conductivity under extreme temperature conditions, which is difficult to obtain in experiments.
主讲人简介
Shouhang Li received his B.S. degree from the School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, China, in 2016. He is currently pursuing his Ph.D. degree in the University of Michigan-Shanghai Jiao Tong Universisty Joint Institute, Shanghai Jiao Tong University, Shanghai, China. His research interests include Nano/Micro heat transfer and electron-phonon interactions.