报告题目：Spin-Dependent Phenomena: From 2D Materials to Lasers

报告人：徐高峰博士

报告时间：2020年12月10日（周四），上午9:30-10:30

报告地点：腾讯会议 https://meeting.tencent.com/s/raHrOQI70oBK

会议ID： 456356514

会议密码：123456

报告摘要：In this talk, I will introduce you my research findings on spin-dependent phenomena in 2D materials and lasers. In many atomically thin materials, their optical absorption is dominated by excitonic transitions. It was recently found that optical selection rules in these materials are influenced by the band topology near the valleys. We propose that gate-controlled band ordering in a single atomic monolayer, through changes in the valley winding number and excitonic transitions, can be probed in helicity-esolved absorption and photoluminescence. This predicted tunable band topology is confirmed by combining an effective Hamiltonian and a Bethe-Salpeter equation for an accurate description of excitons, with first-principles calculations suggesting its realization in Sb-based monolayers.

Lasers have both ubiquitous applications and roles as model systems in which non-equilibrium and cooperative phenomena can be elucidated. The introduction of novel concepts in laser operation thus has potential to lead to both new applications and fundamental insights. Spintronics, in which both the spin and the charge of the electron are used, has led to the development of spin-lasers, in which charge-carrier spin and photon spin are exploited. Here we show that the coupling between carrier spin and light polarization in common semiconductor lasers can enable room-temperature modulation frequencies above 200 gigahertz, exceeding by nearly an order of magnitude the best conventional semiconductor lasers. Surprisingly, this ultrafast operation of the resultant spin-laser relies on a short carrier spin relaxation time and a large anisotropy of the refractive index, both of which are commonly viewed as detrimental in spintronics and conventional lasers. Our results overcome the key speed limitations of conventional directly modulated lasers and offer a prospect for the next generation of low-energy ultrafast optical communication.

报告人简介：徐高峰，纽约州立大学布法罗分校博士后。本科毕业于西北大学物理系，后在香港中文大学物理系获硕士学位，博士毕业于纽约州立大学布法罗分校，在凝聚态物理和量子光学两个领域开展理论研究，在Nature，Physical Review Letters，Physical Review A，Physical Review B等期刊发表论文共7篇。作为骨干研究成员，参与完成了美国National Science Foundation和美国能源部等机构支持的多个科研项目，在二维材料中激子相关的光学性质、半导体自旋激光器在超快激光通信中的应用及腔光力学等研究方向取得成果。

学院联系人：李源