Exotic response in topological materials
Abstract: The 2016 nobel prize in physics was awarded to topological phase transitions and topological phase of matter. In this talk I will briefly review the BKT topological transition of vortex and anti-vortex states and the TKNN formula in the explanation of the quantization of Hall conductivity. We use the Green's function technique and Kubo formula to study the spectral function, density of states, optical and magneto-optical conductivity in topological insulators and valleytronic materials. In general the Kubo formula can also be generalized to study nonlinear response to the external driving electro-magnetic field E or B. One example was given in our study of the nonlinear magneto-optical conductivity for topological insulators in which the particle-hole asymmetry can generate chiral absorption of left and right circularly polarized light. Recently we study the nonlinear response (frequency up- and down-conversion) to an electric field E and found an unusual way to generate a DC current from frequency down-conversion. This may bring novel nonlinear thermoelectric functionalities (e.g. thermal energy harvesting) in the far-infrared region. We also studied the time evolution of a Gaussian wave packet in a flat-band system with disorder-induced depasing and decay of quantum states.
Speaker： 李舟，2004年本科毕业于南京大学物理系，2007年硕士毕业于北京大学物理系，2012年博士毕业于加拿大阿尔伯塔大学物理系。在加拿大攻读博士学位期间曾获得Alberta Ingenuity奖学金，博士毕业时获得阿尔伯塔省政府颁发的Andrew Steward毕业纪念奖和阿尔伯塔大学毕业论文奖，同时获得由中国驻温哥华总领馆颁发的国家优秀自费留学生奖。先后在加拿大McMaster University，美国Louisiana state university从事博士后研究工作，在APS March Meeting等国际会议做邀请报告。现在是日本理化学研究所由日本政府资助的JSPS学者。