Xu Shengnan, Si Chen, Li Yang, Gu Bing-Lin, Duan Wenhui
State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China.
Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China.
Nano Lett. 2021 Feb 24;21(4):1785-1791. doi: 10.1021/acs.nanolett.0c04670. Epub 2021 Feb 15.
The valley depolarization dynamics of free holes in monolayer transition-metal dichalcogenides are studied by solving the Boltzmann transport equation in real time fully . While monolayer MoSe, WS, WSe, and MoTe possess long hole valley lifetimes due to the spin-valley locking effect, monolayer MoS unexpectedly shows ultrafast valley dynamics, with a hole valley lifetime two orders of magnitude shorter than those of the above four materials at room temperature. It is further revealed that the existence of the satellite Γ valley in MoS provides an additional hole relaxation path where the Γ valley acts as an intermediate in the hole relaxation between primary K' and K valleys, and moreover, the strong scattering between primary and satellite valleys ensures the ultrafast valley depolarization. By uncovering the pivotal role of the satellite valley, our results may have significant implications for finely controlling valley depolarization in the multivalley materials.
通过实时完全求解玻尔兹曼输运方程，研究了单层过渡金属二硫属化物中自由空穴的谷去极化动力学。虽然由于自旋-谷锁定效应，单层MoSe₂、WS₂、WSe₂和MoTe₂具有较长的空穴谷寿命，但单层MoS₂出人意料地表现出超快的谷动力学，在室温下其空穴谷寿命比上述四种材料短两个数量级。进一步研究发现，MoS₂中卫星Γ谷的存在提供了一条额外的空穴弛豫路径，其中Γ谷在主要K'和K谷之间的空穴弛豫中起中间作用，而且，主要谷和卫星谷之间的强散射确保了超快的谷去极化。通过揭示卫星谷的关键作用，我们的结果可能对精细控制多谷材料中的谷去极化具有重要意义。
