二维层状纳米材料的谷极化与谷电子/自旋弛豫动力学研究

类石墨烯新型二维层状原子晶体材料由于其独特的光、电性质，构筑了谷电子学、光电子学与自旋电子学的应用桥梁，近年来引起物理、化学、材料、电子等众多领域研究人员的广泛关注。本申请项目拟以机械剥离的掺杂或者非掺杂单层、双层和多层新型二维层状原子晶体材料WSe2、MoS2等为研究对象，通过对其激子及其荧光性质和能谷极化响应的研究，以及谷极化、谷电子/自旋在不同温度、光激发波长（能量）与功率密度，以及外场和材料设计调控下的弛豫动力学过程研究，以期获得谷内与谷间电子－电子散射、电－声子散射，以及电子－空穴交换耦合、自旋－轨道耦合、材料缺陷和无序等影响激子复合寿命、谷极化寿命和谷电子/自旋寿命的信息，从而对激子辐射复合发光动力学过程以及激子、谷电子/自旋弛豫过程和相应的物理机制有深入的理解，为实现基于二维原子晶体谷电子功能的新型光电器件和自旋电子器件奠定基础。

In recent years, the graphene-like novel two dimensional (2D) layered transition metal dichalcogenides, such as MoS2 and WSe2, have attracted great attention in the research fields of physics, chemistry, material, electronics so on due to their novel electronic and optical properties. The 2D layered crystalline materials build the bridge between the valleytronics and optoelectronics, as well as the spintronics. This proposal will focus on the doped or undoped monolayer, bilayer and few-layer 2D crystalline materials fabricated by the mechanical exfoliation with adhesive tape from bulk crystals onto 300nm-thick SiO2 on Si substrates. The exciton and related photoluminescence properties as well as the valley polarization controlled by excitation light helicity will be investigated first, then the ultrafast dynamics of the valley polarization, valley electron/spin at different temperature, excitation wavelength and power density, external fields, as well as different material design will be further investigated experimentally in detail. The studied key physics is the influence of intravalley and intervalley electron-electron scattering, electron-phonon scattering; and the electron-hole exchange interaction, spin-orbit coupling, as well as the defects and disorder of the material on the exciton dynamics and the lifetimes of valley polarization and valley electron/spins. The ultimate goal of this proposal is to understand the fundamental physics of the excitonic radiative dynamics; the information about the lifetimes of valley polarization and valley electron/spins and the related physical mechanisms. The research output of this proposal will be fundamentally important aiming for the development of valley-dependent novel optoelectronics and spintronics based on 2D layered crystalline materials.