Trion Species-Resolved Quantum Beats in MoSe2

TL;DR

This study reveals long-lived coherence and quantum beats between excitons and trions in monolayer MoSe2, demonstrating potential for on-chip quantum photonic applications through linear optical measurements.

Contribution

It provides the first direct linear optical measurement of exciton and trion coherence times in MoSe2, showing prolonged dephasing times and coherent coupling.

Findings

Long dephasing times up to 1.16 ps for trions.

Gate-dependent formation of localized hole trions.

Quantum beats indicating coherent exciton-trion coupling with 0.6 ps dephasing time.

Abstract

Monolayer photonic materials offer a tremendous potential for on-chip optoelectronic devices. Their realization requires knowledge of optical coherence properties of excitons and trions that have so far been limited to nonlinear optical experiments carried out with strongly inhomogenously broadened material. Here we employ h-BN encapsulated and electrically gated MoSe2 to reveal coherence properties of trion-species directly in the linear optical response. Autocorrelation measurements reveal long dephasing times up to T2=1.16+-0.05 ps for positively charged excitons. Gate dependent measurements provide evidence that the positively-charged trion forms via spatially localized hole states making this trion less prone to dephasing in the presence of elevated hole carrier concentrations. Quantum beat signatures demonstrate coherent coupling between excitons and trions that have a dephasing time up to 0.6 ps, a two-fold increase over those in previous reports. A key merit of the prolonged exciton/trion coherences is that they were achieved in a linear optical experiment, and thus are directly relevant to applications in nanolasers, coherent control, and on-chip quantum information processing requiring long photon coherence.