Phonon-assisted oscillatory exciton dynamics in monolayer MoSe2

TL;DR

This study reveals that phonons induce oscillatory behavior in exciton photoluminescence and related properties in monolayer MoSe2, highlighting phonons' crucial role in exciton dynamics in 2D semiconductors.

Contribution

It demonstrates the direct influence of LA(M) phonons on exciton photoluminescence oscillations and exciton lifetime variations in monolayer MoSe2.

Findings

Oscillatory enhancement of exciton photoluminescence with excitation energy.

Oscillations match the LA(M) phonon frequency.

Variation in exciton lifetime linked to phonon interactions.

Abstract

In monolayer semiconductor transition metal dichalcogenides, the exciton-phonon interaction is expected to strongly affect the photocarrier dynamics. Here, we report on an unusual oscillatory enhancement of the neutral exciton photoluminescence with the excitation laser frequency in monolayer MoSe2. The frequency of oscillation matches that of the M-point longitudinal acoustic phonon, LA(M). Oscillatory behavior is also observed in the steady-state emission linewidth and in timeresolved photoluminescence excitation data, which reveals variation with excitation energy in the exciton lifetime. These results clearly expose the key role played by phonons in the exciton formation and relaxation dynamics of two-dimensional van der Waals semiconductors.