Asymmetric Valley Polarization of Excitons and Trions in Antiferromagnet-Semiconductor MoSe₂/CrI₃ Heterostructures.

Abstract

Magnetic proximity interactions in van der Waals heterostructures offer a distinct means for controlling over spin and valley properties of nonmagnetic monolayers, such as transition metal dichalcogenides (TMDs). An essential aspect is to manipulate the valley-polarized excitons in TMDs through spin-polarized electron hopping at the heterointerface. While the notion of electron hopping channels well illustrates the circularly polarized photon emission, it obscures the fact that spin coupling between the magnetic layers and various excitonic states (such as neutral excitons and trions) in the TMDs could be substantially different. Individual addressing and manipulation of different excitonic valley polarizations remain challenging so far. Herein, we show that the valley polarization of excitons and trions can actually be asymmetric in the MoSe₂/CrI₃ heterostructure, which is triggered by the disequilibrium of intervalley excitonic conversion. The model is experimentally verified by temperature-dependent and magnetic-field-dependent polarization degrees, while the valley polarization dynamics is quantitatively fitted by the differential equation of excitonic population with intervalley conversion and scattering processes included. Finally, we demonstrate all-optical manipulation of valley polarization. Our studies provide routes to achieve dual-valley pseudospin processing channels, opening up opportunities for excitonic spin information processing in magneto-optoelectronic devices.