标题： 超快全光纯自旋和谷电流的产生 显示英文标题

标题： Ultrafast all-optical generation of pure spin and valley currents

摘要： 纯电流由二维量子自由度（例如电子自旋）的流动组成，而没有电荷流。 与支撑当今电子学的电荷电流截然不同，在具有额外二维状态自由度（如谷指数）的二维材料中，它们为下一代自旋和谷电子学提供了显著的微型化和能效可能性。 在这里，我们展示了一种稳健的多泵浦光波协议，能够在飞秒时间内生成纯自旋和谷电流。 生成时间由二维材料带隙决定，在WSe2中纯自旋电流的产生时间为40 fs，在双层石墨烯中纯谷电流的产生时间为约200 fs。 我们的全光方法不需要特殊材料设计，只需要一个带隙谷活性材料，因此适用于广泛的二维材料。 显示英文摘要

摘要： Pure currents comprise the flow of a two state quantum freedom -- for example the electron spin -- in the absence of charge flow. Radically different from the charge currents that underpin present day electronics, in two dimensional materials possessing additional two state freedoms such as valley index they offer profound possibilities for miniaturization and energy efficiency in a next generation spin- and valley- tronics. Here we demonstrate a robust multi-pump light wave protocol capable of generating both pure spin and valley currents on femtosecond times. The generation time is determined by the 2d material gap, with the creation of pure spin current in WSe2 at 40 fs and pure valley current in bilayer graphene at ~200 fs. Our all-optical approach demands no special material design, requiring only a gapped valley active material, and is thus applicable to a wide range of 2d materials.