Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA.
Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea.
Science. 2018 May 25;360(6391):893-896. doi: 10.1126/science.aao3503. Epub 2018 May 24.
Transition metal dichalcogenide (TMDC) materials are promising for spintronic and valleytronic applications because valley-polarized excitations can be generated and manipulated with circularly polarized photons and the valley and spin degrees of freedom are locked by strong spin-orbital interactions. In this study we demonstrate efficient generation of a pure and locked spin-valley diffusion current in tungsten disulfide (WS)-tungsten diselenide (WSe) heterostructures without any driving electric field. We imaged the propagation of valley current in real time and space by pump-probe spectroscopy. The valley current in the heterostructures can live for more than 20 microseconds and propagate over 20 micrometers; both the lifetime and the diffusion length can be controlled through electrostatic gating. The high-efficiency and electric-field-free generation of a locked spin-valley current in TMDC heterostructures holds promise for applications in spin and valley devices.
过渡金属二卤族化合物（TMDC）材料在自旋电子学和谷电子学应用中具有广阔的前景，因为可以通过圆偏振光子产生和操纵谷极化激子，并且强自旋轨道相互作用锁定了谷和自旋自由度。在本研究中，我们展示了在没有任何驱动电场的情况下，在二硫化钨（WS）-二硒化钨（WSe）异质结构中高效产生纯且锁定的自旋谷扩散电流。我们通过泵浦探测光谱实时和空间成像了谷电流的传播。异质结构中的谷电流可以持续超过 20 微秒并传播超过 20 微米；通过静电门控可以控制寿命和扩散长度。在 TMDC 异质结构中高效且无需电场的锁定自旋谷电流的产生为自旋和谷器件的应用提供了可能。
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