Department of Electrical Engineering , Stanford University , Stanford , California 94305 , United States.
Department of Electrical and Computer Engineering , University of Texas at Austin , Austin , Texas 78712 , United States.
Nano Lett. 2019 Feb 13;19(2):770-774. doi: 10.1021/acs.nanolett.8b03838. Epub 2019 Jan 2.
We investigate the valley Hall effect (VHE) in monolayer WSe field-effect transistors using optical Kerr rotation measurements at 20 K. While studies of the VHE have so far focused on n -doped MoS, we observe the VHE in WSe in both the n - and p -doping regimes. Hole doping enables access to the large spin-splitting of the valence band of this material. The Kerr rotation measurements probe the spatial distribution of the valley carrier imbalance induced by the VHE. Under current flow, we observe distinct spin-valley polarization along the edges of the transistor channel. From analysis of the magnitude of the Kerr rotation, we infer a spin-valley density of 44 spins/μm, integrated over the edge region in the p -doped regime. Assuming a spin diffusion length less than 0.1 μm, this corresponds to a spin-valley polarization of the holes exceeding 1%.
我们使用 20 K 时的光学克尔旋转测量研究了单层 WSe 场效应晶体管中的谷霍尔效应（VHE）。虽然迄今为止对 VHE 的研究都集中在 n 型掺杂的 MoS 上，但我们在 n 型和 p 型掺杂区都观察到了 WSe 中的 VHE。空穴掺杂使我们能够获得该材料价带大的自旋劈裂。克尔旋转测量探测了 VHE 引起的谷载流子不平衡的空间分布。在电流作用下，我们观察到在晶体管沟道的边缘处存在明显的自旋 - 谷极化。从克尔旋转的幅度分析中，我们推断出在 p 型掺杂区边缘区域的自旋 - 谷密度为 44 自旋/μm。假设自旋扩散长度小于 0.1 μm，这对应于超过 1%的空穴自旋 - 谷极化。
