Twisted-light-induced exciton wave packets in transition-metal dichalcogenide monolayers

TL;DR

This paper theoretically explores how twisted light beams induce localized exciton wave packets in transition-metal dichalcogenide monolayers, revealing new ways to control and detect excitonic states via optical orbital angular momentum.

Contribution

It introduces a comprehensive model of twisted-light-induced exciton wave packets in TMD monolayers, highlighting their directional emission and valley-selective detection capabilities.

Findings

Exciton wave packets are spatially localized and depend on optical OAM.

Directional photoluminescence patterns encode transferred optical OAM.

Linearly polarized twisted light enables valley-specific exciton detection.

Abstract

We present a comprehensive theoretical investigation of the photo-generated excitons in transition-metal dichalcogenide monolayers (TMD-ML's) by Laguerre-Gaussian beams, a celebrated kind of twisted lights (TL's) carrying quantized orbital angular momenta (OAM). We show that the photo-excitation of TL incident to a TMD-ML leads to the formation of spatially localized exciton wave packets, constituted by the superposition of finite-momentum exciton states determined by the intriguing interplay between the multiple degrees of freedom of the optical and excitonic subsystems. Consequently, the TL-induced exciton wave packets yield profound directional photo-luminescences whose polar-angle-dependences are encoded by the transferred optical OAM and azimuthal angle part, despite OAM-irrelevant, optically resolves the exchange-split longitudinal and transverse exciton bands. Interestingly, the application of linearly polarized TL onto a valley-excitonic system mimics an exciton multiplexer allowing for selectively detecting the individual valley-mixed exciton bands, which are normally hardly measured spectrally.