Yu Hongyi, Wang Yong, Tong Qingjun, Xu Xiaodong, Yao Wang
Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong, China.
Department of Physics, University of Washington, Seattle, Washington 98195, USA.
Phys Rev Lett. 2015 Oct 30;115(18):187002. doi: 10.1103/PhysRevLett.115.187002.
We show that, because of the inevitable twist and lattice mismatch in heterobilayers of transition metal dichalcogenides, interlayer excitons have sixfold degenerate light cones anomalously located at finite velocities on the parabolic energy dispersion. The photon emissions at each light cone are elliptically polarized, with the major axis locked to the direction of exciton velocity, and helicity specified by the valley indices of the electron and the hole. These finite-velocity light cones allow unprecedented possibilities for optically injecting valley polarization and valley current, and the observation of both direct and inverse valley Hall effects, by exciting interlayer excitons. Our findings suggest potential excitonic circuits with valley functionalities, and unique opportunities to study exciton dynamics and condensation phenomena in semiconducting 2D heterostructures.
我们表明，由于过渡金属二卤化物异质双层中不可避免的扭曲和晶格失配，层间激子具有六重简并光锥，这些光锥异常地以有限速度位于抛物线能量色散上。每个光锥处的光子发射是椭圆偏振的，其主轴锁定在激子速度方向上，并且螺旋度由电子和空穴的能谷指数指定。这些有限速度的光锥为通过激发层间激子来光学注入能谷极化和能谷电流，以及观察直接和逆能谷霍尔效应提供了前所未有的可能性。我们的发现表明了具有能谷功能的潜在激子电路，以及研究半导体二维异质结构中激子动力学和凝聚现象的独特机会。
