Tailoring the superposition of finite-momentum valley exciton states in transition-metal dichalcogenide monolayers by using polarized twisted light

Abstract

A twisted light is a spatially structured light that carries quantized orbital angular momenta (OAM), being a new degree of freedom useful in quantum information technology in addition to that of intrinsic spin angular momentum (SAM), i.e., polarization. Using polarized twisted light to excite valley excitons in transition-metal dichalcogenide monolayers (TMD-ML's) sets up an intriguing photoexcited system which couples comprehensively the excitonic and photonic multi-degrees of freedom, including the center-of-mass motion and valley polarization of exciton and the both optical OAM and SAM. In this work, we present a systematic theoretical investigation of the photoexcited valley excitons in TMD-ML's by polarized Laguerre-Gaussian beams, one of the best known twisted light (TL). We show that the photoexcitation of polarized TL incident to a TMD-ML leads to the formation of the superposition of finite-momentum exciton (SFME) states, spatially localized with the OAM- and SAM-encoded geometrical patterns.