报告时间：2024年3月27日（周三）下午2:00
报告地点：仲英楼B243会议室
报告人简介：董珊，半导体研究所特别研究助理，合作导师为常凯院士，博士毕业于北京理工大学，姚裕贵教授课题组，导师为李元昌教授。主要研究方向为：1.二维材料激子绝缘体的第一性原理计算。2.固体氧化物燃料电池阳极结构的催化，模拟及设计。已在国际著名期刊发表文章9篇，其中第一作者发表论文7篇（Phys．Rev．B（3篇），Phys．Chem．Chem．Phys, Applied Surface Science和J Phys.Chem．C等）。主持包括“中科院特别研究助理资助”，“中国博士后科学基金特别资助”，“国家自然科学基金理论物理专项资助”，半导体研究所“青年科技人才推进计划项目”等项目，共一百余万。在第六届“凝聚态物质中的激发态”会议作邀请报告，获“ExcellentYoung Scholars”奖。
Abstract:
Excitonic insulator is a macroscopic quantum state in a manner analogous to superconductor theoretically proposed by Nobel Prize winners Mott and Kohn, and other physicist in 1960s. It exists when the exciton binding energy exceeds the excitation energy gap and is a spontaneous exciton Bose-Einstein condensate. Understanding the behavior of excitonic insulator can not only provide enlightenment for superconductivity, superfluidity and other supertransport phenomena, but also have broad application prospects in quantum computing and new photoelectric devices. In this talk, I will discuss two candidate materials for excitonic insulators which are newly synthesized in the experiment. Firstly, it is predicted that two dimensional AlSb is an intrinsic excitonic insulator. GW-BSE calculation shows that the exciton binding energy exceeds the one-electron gap by about 0.1 eV, which indicates the spontaneous generation of excitons. Secondly, we propose the band insulator - excitonic insulator transition through alloy. Stimulated by the recent successful preparation of TiS3-xSexalloy by Se doping in TiS3. Besides, we also find a new topological state - topological exciton insulator. We verify this by first-principles calculations on monolayer transition-metal carbides, which show a robust thermal-equilibrium exciton condensation, being sufficient for topological applications at room temperature. Our work provides not only a guide for finding more topological excitonic insulators, but also a new platform for studying the interplay between nontrivial band topology and quantum many-body effects.
Keywords:Excitonic insulator, exciton, GW-BSE, first-principlescalculation,two-dimensional materials
References:
[1]Dong S; Li Y.Phys. Rev. B, 102 (15): 155119 (2020).
[2]Dong S; Li Y.Phys. Rev. B, 107 : 235147 (2023).
[3]Dong S; Li Y.Phys. Rev. B, 104(8) : 085133 (2021).
[4]L. Du, X. Li, W. Lou, G. Sullivan, K. Chang, J. Kono and R. R. Du,Nat. Commun.8, 1-8 (2017).
