Ren L, Lombez L, Robert C, Beret D, Lagarde D, Urbaszek B, Renucci P, Taniguchi T, Watanabe K, Crooker S A, Marie X
Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077 Toulouse, France.
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-00044, Japan.
Phys Rev Lett. 2022 Jul 8;129(2):027402. doi: 10.1103/PhysRevLett.129.027402.
Using a spatially resolved optical pump-probe experiment, we measure the lateral transport of spin-valley polarized electrons over very long distances (tens of micrometers) in a single WSe_{2} monolayer. By locally pumping the Fermi sea of 2D electrons to a high degree of spin-valley polarization (up to 75%) using circularly polarized light, the lateral diffusion of the electron polarization can be mapped out via the photoluminescence induced by a spatially separated and linearly polarized probe laser. Up to 25% spin-valley polarization is observed at pump-probe separations up to 20 μm. Characteristic spin-valley diffusion lengths of 18±3 μm are revealed at low temperatures. The dependence on temperature, pump helicity, pump intensity, and electron density highlight the key roles played by spin relaxation time and pumping efficiency on polarized electron transport in monolayer semiconductors possessing spin-valley locking.
通过空间分辨光泵浦-探测实验，我们测量了单个WSe₂单层中自旋-谷极化电子在很长距离（数十微米）上的横向输运。利用圆偏振光将二维电子的费米海局部泵浦到高度的自旋-谷极化（高达75%），电子极化的横向扩散可以通过空间分离的线偏振探测激光诱导的光致发光来描绘。在泵浦-探测间距高达20μm时，观察到高达25%的自旋-谷极化。在低温下揭示了18±3μm的特征自旋-谷扩散长度。对温度、泵浦螺旋度、泵浦强度和电子密度的依赖性突出了自旋弛豫时间和泵浦效率在具有自旋-谷锁定的单层半导体中极化电子输运中所起的关键作用。
