Realization of Valley and Spin Pumps by Scattering at Nonmagnetic Disorders.
Realization of Valley and Spin Pumps by Scattering at Nonmagnetic Disorders.
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DOI：
10.1103/physrevlett.118.096602
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发表时间：
2016-02
影响因子：
8.6
通讯作者：
Xing-Tao An;Jiang Xiao;M. Tu;Hongyi Yu;V. Fal’ko;W. Yao
中科院分区：
文献类型：
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作者：
Xing-Tao An;Jiang Xiao;M. Tu;Hongyi Yu;V. Fal’ko;W. Yao
最近在二维过渡金属二硫族化合物（TMDs）中谷偏振光泵浦的成功极大地促进了基于谷的信息学和电子学的概念。然而，在证明的瞬态电子-空穴对激发的谷极化与实际的谷电子操作之间，存在着明显的空白需要填补，其中之一就是长寿命载流子的谷泵浦。在这里，我们发现所追求的电子或空穴的谷泵可以简单地通过在无处不在的非磁性障碍上散射来实现，而不依赖于任何特定的材料特性。该机制植根于谷作为动量空间指数的性质：由于不同的动量转移，谷间后向散射通常具有谷对比率，导致人口从一个谷到另一个谷的净转移。作为例子，我们数值证明了电荷流驱动单层tmd纳米带中可观的谷泵效应，其中非磁性障碍引起的自旋轨道散射也实现了自旋谷锁孔的自旋泵。我们的发现为谷自旋电子学提供了一个新的机会，将失调从一个有害因素转变为谷和自旋极化的资源。
The recent success in optical pumping of valley polarization in two-dimensional transition metal dichalcogenides (TMDs) has greatly promoted the concept of valley-based informatics and electronics. However, between the demonstrated valley polarization of transient electron-hole pair excitations and practical valleytronic operations, there exist obvious gaps to fill, among which is the valley pump of long-lived charge carriers. Here we discover that the quested valley pump of electrons or holes can be realized simply by scattering at the ubiquitous nonmagnetic disorders, not relying on any specific material property. The mechanism is rooted in the nature of the valley as a momentum space index: the intervalley backscattering in general has a valley contrasted rate due to the distinct momentum transfers, causing a net transfer of population from one valley to another. As examples, we numerically demonstrate the sizable valley pump effects driven by charge current in nanoribbons of monolayer TMDs, where the spin-orbit scattering by nonmagnetic disorders also realizes a spin pump for the spin-valley locked holes. Our finding points to a new opportunity towards valley spintronics, turning disorders from a deleterious factor to a resource of valley and spin polarization.