报告主题：新型半导体二维物理-从拓扑绝缘体到激子绝缘体

专家姓名：张绳百
报告时间7月1日下午14:30
地点：讲堂群210报告厅

主办单位：理学院

主讲简介：张绳百，1989年毕业于加利福尼亚大学伯克利分校物理学专业，获理学博士学位。1991年-2008年，美国再生能源实验室高级科学家。2008年至今，资深Kodosky星座讲座教授。长期从事凝聚态理论计算和模拟研究工作，在半导体缺陷物理、半导体表面及界面物理、纳米材料设计、室温储氢机制、纳米催化化学、新材料开发等方面取得了重要成绩。在国际重要期刊上发表SCI收录论文300余篇，其中在国际物理类顶级期刊Phys. Rev. Lett.上发表学术论文60余篇，他引2万多次。

主讲内容：I will discuss possible forms of ordinary semiconductors such as GaAs in their two-dimensional (2D) limit. It appears that, regardless the commonly-observed bulk form, a universal van der Waals (vdW) stacking may take place when the film thickness is below a critical thickness. Interestingly, such a vdW stacking can also lead to non-trivial topological properties, as in the case of GaAs. Moreover, the 2D GaAs may become an excitonic insulator with a characteristic exciton binding energy (E_b) larger than the band gap (E_g). More strikingly, in some of the strongly-correlated 2D systems, e.g., MX2 where M = Ni, Co and X = Cl, Br, half excitonic insulator can happen where one spin channel remains to be an ordinary semiconductor whereas the other spin channel will be an excitonic insulator.