Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA.
Nat Nanotechnol. 2012 Aug;7(8):494-8. doi: 10.1038/nnano.2012.96. Epub 2012 Jun 17.
Electronic and spintronic devices rely on the fact that free charge carriers in solids carry electric charge and spin. There are, however, other properties of charge carriers that might be exploited in new families of devices. In particular, if there are two or more minima in the conduction band (or maxima in the valence band) in momentum space, and if it is possible to confine charge carriers in one of these valleys, then it should be possible to make a valleytronic device. Valley polarization, as the selective population of one valley is designated, has been demonstrated using strain and magnetic fields, but neither of these approaches allows dynamic control. Here, we demonstrate that optical pumping with circularly polarized light can achieve complete dynamic valley polarization in monolayer MoS(2) (refs 11, 12), a two-dimensional non-centrosymmetric crystal with direct energy gaps at two valleys. Moreover, this polarization is retained for longer than 1 ns. Our results, and similar results by Zeng et al., demonstrate the viability of optical valley control and suggest the possibility of valley-based electronic and optoelectronic applications in MoS(2) monolayers.
电子和自旋电子器件依赖于这样一个事实，即固体中的自由电荷载流子携带电荷和自旋。然而，电荷载流子还有其他可能在新的器件家族中被利用的特性。特别是，如果在动量空间中导带（或价带中）有两个或更多的最小值（或最大值），并且如果有可能在这些谷值之一中限制电荷载流子，那么就有可能制造出谷电子器件。谷极化，即指定的一个谷的选择性填充，已经使用应变和磁场进行了演示，但是这两种方法都不允许动态控制。在这里，我们证明了使用圆偏振光进行光泵浦可以在单层 MoS2（参考文献 11、12）中实现完全的动态谷极化，这是一种具有两个谷的直接能隙的二维非中心对称晶体。此外，这种极化的保持时间超过 1 ns。我们的结果以及曾等人的类似结果表明，光谷控制是可行的，并暗示了在 MoS2 单层中基于谷的电子和光电子应用的可能性。
