Application of Photoluminescence in the Study of Valley Polarization and Valley Coherence of Two Dimensional Transition Metal Chalcogenides

The discovery of graphene has opened the door to two-dimensional materials, and its special characteristics in energy valley are endowed with extremely high research value. However, the zero band gap of graphene impedes the study of its energy valley properties in optics. As a two-dimensional semiconductor material, transition metal sulfide compounds embrace the characteristics of direct band gap at the low level of monolayer, the space inversion symmetry of the lattice is broken, and the energy valley characteristics are similar to that of graphene. Therefore, it is another excellent two-dimensional material following graphene. In this paper, we start with the study of valley polarization of transition metal chalcogenides in MoS2 monolayer and valley coherence correlation in WSE2 monolayer. We introduce two control methods of high magnetic field and spin injection, and expound the application of photoluminescence spectrum in the study of energy valley properties of two-dimensional layered transition metal chalcogenides.