德州大学奥斯汀分校

报告人简介

Dr. Zhenbang Dai is a computational physicist specialized in condensed matter physics, with a focus on developing and leveraging ab initio methods to investigate complex phenomena in materials, including charged polarons, excitonic polarons, bulk photovoltaic effect, anharmonic lattice dynamics, etc. Currently, Dr. Dai is a postdoctoral researcher in the Oden Institute at University of Texas at Austin. Prior to his current position, he earned the Ph.D. degree from the Department of Chemistry at University of Pennsylvania in 2022, and obtained his B.S. degree in materials science and engineering from Shanghai Jiao Tong University in 2017.

报告摘要

Excitons are neutral excitations that are composed of electrons and holes bound together by their attractive Coulomb interaction. The electron and the hole forming the exciton also interact with the underlying atomic lattice, and this interaction can lead to a trapping potential that favors exciton localization. The quasiparticle thus formed by the exciton and the surrounding lattice distortion is called excitonic polaron. Excitonic polarons have long been thought to exist in a variety of materials, and are often invoked to explain the Stokes shift between the optical absorption edge and the photoluminescence peak. However, quantitative ab initio calculations of these effects are exceedingly rare. In this talk, I will present a theory of excitonic polarons that is amenable to first-principles calculations. I will demonstrate how we can apply this theory to model Hamiltonians for Wannier excitons experiencing Fröhlich or Holstein electron-phonon couplings. We find that, in the case of Fröhlich interactions, excitonic polarons only form when there is a significant difference between electron and hole effective masses. Then, I will show its first principles implementation to calculate excitonic polarons in lithium fluoride. The key advantage of the present approach is that it does not require supercells, therefore it can be used to study a variety of materials hosting either small or large excitonic polarons. This work constitutes the first step toward a complete ab initio many-body theory of excitonic polarons in real materials.

腾讯会议号：683 835 394 

密码：240307 

邀请人：廉   超 副研究员

联系人：万   源 研究员

          汪非凡 副研究员

          田春璐  cltian@iphy.ac.cn

主办方：滚球自动投注、松山湖材料实验室