Anomalous Light Cones and Valley Optical Selection Rules of Interlayer Excitons in Twisted Heterobilayers

• DOI: 10.1103/physrevlett.115.187002
• Publication Date: 2015-10-30T17:08:30Z
• Authors: Hongyi Yu; Yong Wang; Qingjun Tong; Xiaodong Xu; Wang Yao
• Keywords: Boron Compounds; 0301 basic medicine; Condensed Matter - Materials Science; Condensed Matter - Mesoscale and Nanoscale Physics; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 02 engineering and technology; Tungsten Compounds; 7. Clean energy; 03 medical and health sciences; Models, Chemical; Hardness; Tensile Strength; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 0210 nano-technology; Boron

We show that, because of the inevitable twist and lattice mismatch in heterobilayers of transition metal dichalcogenides, interlayer excitons have six-fold degenerate light cones anomalously located at finite velocities on the parabolic energy dispersion. The photon emissions at each light cone are elliptically polarized, with 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 to optically inject 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.<br/>Including the Supplemental Materials<br/>