Unravelling the coupling between excitonic quasiparticles-electron-phonon and role of interlayer coupling in vertically and horizontally aligned layered MoS2

TL;DR

This study investigates excitonic quasiparticles and their interactions with phonons in vertically and horizontally aligned MoS2, revealing how interlayer coupling and temperature influence optical properties and exciton dynamics.

Contribution

It provides new insights into exciton-trion-phonon coupling and the role of interlayer interactions in aligned MoS2, highlighting temperature-dependent effects on electronic structure.

Findings

Trion signatures persist up to 330 K in both systems.

Vertical alignment shows greater impact on exciton dynamics and valence band splitting.

Temperature increases lead to linewidth broadening mainly due to phonons.

Abstract

Excitonic quasi-particles, excitons/trions/bi-excitons, and their coupling with phonons and charge carriers play a crucial role in controlling the optical properties of atomically thin semiconducting 2D materials. In this work, we unravelled the dynamics of excitons/trions and their coupling with phonons and charge carriers in a few layers vertically and horizontally aligned MoS2. We observed trion signature up to the highest recorded temperature (330 K) in both systems and have shown that the dynamics of excitons/trions and their coupling with phonons and electrons are more affected in vertically aligned MoS2. A homogeneous linewidth broadening is observed with an increase in temperature. The linewidth broadening is attributed mainly to acoustic phonons in a low-temperature regime (<100 K). In contrast, acoustic and longitudinal optical phonons contributions to the linewidth broadening are observed at high temperature. We also observed the significant effects of interlayer coupling in both systems via understanding the temperature-dependent valence band splitting and trion binding energy. A decrease of 22 and 12% in valence band splitting with temperature rise is observed for the vertically and horizontally aligned MoS2, respectively, suggesting that the valence band splitting is affected more in the case of vertically than horizontally aligned. Furthermore, we also notice a significant thermal quenching in the intensity of the trion band than that of exciton bands, attributed to the small binding energy of the trion.