Zhang Xiao-Xiao, Lai You, Dohner Emma, Moon Seongphill, Taniguchi Takashi, Watanabe Kenji, Smirnov Dmitry, Heinz Tony F
Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
Phys Rev Lett. 2019 Mar 29;122(12):127401. doi: 10.1103/PhysRevLett.122.127401.
The control of the valley degree of freedom lies at the core of interest in monolayer transition metal dichalcogenides, where specific valley-spin excitation can be created using circularly polarized light. Measurement and manipulation of the valley index has also been achieved, but mainly with purely optical methods. Here, in monolayer MoS_{2}, we identify a response to the valley polarization of excitons in the longitudinal electrical transport when the valley degeneracy is broken by an out-of-plane magnetic field B_{z}. The spin information is also simultaneously determined with spin-sensitive contacts. In the presence of B_{z}, a significant modulation of the photocurrent is observed as a function of the circular polarization state of the excitation. We attribute this effect to unbalanced transport of valley-polarized trions induced by the opposite Zeeman shifts of two (K and K^{'}) valleys. Our interpretation is supported by the contrasting behavior in bilayer MoS_{2}, as well as the observed doping and spatial dependence of the valley photocurrent.
对谷自由度的控制是单层过渡金属二硫属化物研究的核心关注点，在这种材料中，可以使用圆偏振光产生特定的谷自旋激发。谷指数的测量和操纵也已实现，但主要是通过纯光学方法。在此，在单层二硫化钼中，当谷简并被面外磁场Bz打破时，我们确定了在纵向电输运中对激子谷极化的响应。自旋信息也通过自旋敏感接触同时确定。在存在Bz的情况下，观察到光电流随激发圆偏振态的显著调制。我们将这种效应归因于由两个（K和K'）谷的相反塞曼位移引起的谷极化三重子的不平衡输运。我们的解释得到了双层二硫化钼中对比行为以及观察到的谷光电流的掺杂和空间依赖性的支持。
