报告题目：拓扑半金属的非线性光响应及其在高性能光电探测方面的应用
摘要：The experimental manifestation of topological effects in bulk materials under ambient conditions, especially those with practical applications, has attracted enormous research interest. Weyl semimetals and chiral Fermions supply ideal material platforms for such endeavors. The Berry curvature in these materials becomes singular at the node points, creating an effective magnetic monopole in the k-space. Such singular topology can have profound impact on the nonlinear optical response of these materials and it is directly applicable to photodetection. In this talk, we started with our experimental work on the revealing of the singular topology in a type-II Weyl semimetal TaIrTe4 in the photo responses, which is shown to be directly related to the divergence of Berry curvature. As a result of the divergence of Berry curvature at the Weyl nodes, TaIrTe4 exhibits unusually large photo responsivity of 130.2 mA/W with 4-mm excitation in an unbiased field effect transistor at room temperature arising from the third-order nonlinear optical response [1]. We further elucidate such effect is directly applicable to high performance photodetectors based on topological semimetals, especially for long wavelength (low photon energy) range [2]. Some recent progresses along this direction from our group will be discussed. Especially that I will show detectors based on TaIrTe4 are directly sensitive to multiple light parameters, including polarization and orbital angular momentum, in mid-infrared wavelength range [3].
Reference: [1] Nature Materials, 18,476 (2019) [2] Nano Letters 17, 834 (2017); Nature Materials 19,830 (2020) [3] Advanced Materials 30, 1707152 (2018); ACS Nano 12,4055 (2018); arXiv:2202.07873(2022)
报告人简介：孙栋，北京大学量子材料中心长聘副教授，研究员。2004年本科毕业于中 国科学技术大学物理系，2009年博士毕业于密歇根大学超快光科学中心， 然后分别在密歇根大学超快光科学中心和华盛顿大学担任博士后和研究 员，2012年入选海外人才计划青年项目，并受聘北京大学量子材料科学 中心，2017晋升长聘职位，2019年获得北京市杰出青年基金支持。主要 研究方向量子材料的物性以及基于量子材料的光电器件的光谱表征。
