单层 WS 中存在大的、仅谷区的 Bloch-Siegert 位移。
Large, valley-exclusive Bloch-Siegert shift in monolayer WS.
机构信息
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Department of Physics and Astronomy, University of California, Riverside, CA 92521, USA.
出版信息
Science. 2017 Mar 10;355(6329):1066-1069. doi: 10.1126/science.aal2241.
Coherent interaction with off-resonance light can be used to shift the energy levels of atoms, molecules, and solids. The dominant effect is the optical Stark shift, but there is an additional contribution from the so-called Bloch-Siegert shift that has eluded direct and exclusive observation in solids. We observed an exceptionally large Bloch-Siegert shift in monolayer tungsten disulfide (WS) under infrared optical driving. By controlling the light helicity, we could confine the Bloch-Siegert shift to occur only at one valley, and the optical Stark shift at the other valley, because the two effects obey opposite selection rules at different valleys. Such a large and valley-exclusive Bloch-Siegert shift allows for enhanced control over the valleytronic properties of two-dimensional materials.
相干与非共振光相互作用可用于移动原子、分子和固体的能级。主要效应是光斯塔克移动，但固体中还有一种所谓的布洛赫-西格尔特移动，它一直难以被直接和排他性地观察到。我们在单层二硫化钨（WS）中观察到了非常大的布洛赫-西格尔特移动，在红外光驱动下发生。通过控制光的螺旋度，我们可以使布洛赫-西格尔特移动仅在一个谷中发生，而在另一个谷中发生光斯塔克移动，因为这两种效应在不同的谷中遵循相反的选择定则。如此大的且谷特有的布洛赫-西格尔特移动可以增强对二维材料谷电子特性的控制。
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