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Ultrafast exciton dynamics in semiconductor 2D materials

Date: 2022-12-28
Time: 10:00
Venue: Tencent Meeting
Speaker: 董朔

Fritz Haber Institute of the Max Planck Society 博 士




Time- and angle-resolved photoemission spectroscopy (trARPES) is a spectroscopic tool accessing excited states, including quasi-free charge carriers and excitons, in energy-momentum space and on ultrafast timescales, I(Ekin,kx,ky,t). It provides the unique perspective of momentum-forbidden‘dark’states in two-dimensional layer materials, which are critical to understanding the fundamental optoelectronic performances and designing novel devices based on van der Waals (vdW) heterostructures. Using multidimensional photoemission spectroscopy, all key microscopic quantities of excitonic states can be directly revealed at once in the layered transition metal dichalcogenide semiconductor WSe2. Next, I will present the study of two fundamental interfacial interactions within vdW heterostructures monolayer WSe2/graphene: interlayer changed carrier transfer, and excitonic energy transfer. A novel interfacial Meitner-Auger energy transfer process is established, which describes the conversion of an exciton in the semiconductor to an intraband electron-hole pair in graphene. This ultrafast energy conversion leads to the excitation of deep-lying valence holes in the graphene layer, which is particularly interesting for hot-carrier photovoltaics and optoelectronic device concepts.


董朔博士本科毕业于吉林大学,博士毕业于新加坡南洋理工大学,目前在柏林Fritz-Haber Institute马普所开展博后工作,期间设计和重建了一套新型的时间和角度分辨光电子能谱系统:利用高频极紫外激光源与国际先进的动量显微镜检测器,从时间(t)、动量平面(kx,ky)和能量(E)四个维度解析新型二维材料中瞬态电子、激子结构。在二维半导体过渡金属二硫化物,如WSe2和德华异质结构WSe2/graphene中,直接测量出多个关键的激子特性,并发现一种新型层间能量传输机制,为实现原子级层厚二维热载流子的器件提供了坚实的物理基础。

邀 请 人:滕 浩 研究员

联 系 人:王慧颖