Dey P, Yang Luyi, Robert C, Wang G, Urbaszek B, Marie X, Crooker S A
National High Magnetic Field Laboratory, Los Alamos National Lab, Los Alamos, New Mexico 87545, USA.
Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France.
Phys Rev Lett. 2017 Sep 29;119(13):137401. doi: 10.1103/PhysRevLett.119.137401. Epub 2017 Sep 27.
Using time-resolved Kerr rotation, we measure the spin-valley dynamics of resident electrons and holes in single charge-tunable monolayers of the archetypal transition-metal dichalcogenide (TMD) semiconductor WSe_{2}. In the n-type regime, we observe long (∼130 ns) polarization relaxation of electrons that is sensitive to in-plane magnetic fields B_{y}, indicating spin relaxation. In marked contrast, extraordinarily long (∼2 μs) polarization relaxation of holes is revealed in the p-type regime, which is unaffected by B_{y}, directly confirming long-standing expectations of strong spin-valley locking of holes in the valence band of monolayer TMDs. Supported by continuous-wave Kerr spectroscopy and Hanle measurements, these studies provide a unified picture of carrier polarization dynamics in monolayer TMDs, which can guide design principles for future valleytronic devices.
利用时间分辨克尔旋转，我们测量了典型过渡金属二硫族化物（TMD）半导体WSe₂的单电荷可调谐单层中驻留电子和空穴的自旋-谷动力学。在n型区域，我们观察到电子的长（约130 ns）极化弛豫，其对平面内磁场By敏感，表明存在自旋弛豫。与之形成鲜明对比的是，在p型区域发现空穴具有极长（约2 μs）的极化弛豫，且不受By影响，这直接证实了长期以来关于单层TMD价带中空穴强自旋-谷锁定效应的预期。在连续波克尔光谱和汉勒测量的支持下，这些研究提供了单层TMD中载流子极化动力学的统一图景，可为未来谷电子学器件的设计原则提供指导。
