Prediction of Hot Zone-center Optical Phonons in Laser Irradiated Molybdenum Disulfide with a Semiconductor Multitemperature Model

TL;DR

This paper develops a semiconductor-specific multitemperature model to analyze phonon energy relaxation in laser-irradiated MoS2, revealing significant nonequilibrium between zone-center optical phonons and other modes influenced by laser spot size and substrate interaction.

Contribution

The study introduces a new SC-MTM that incorporates electron-hole dynamics and predicts phonon mode nonequilibrium in MoS2, differing from previous polarization-level models.

Findings

No polarization-based nonequilibrium observed in MoS2

Significant nonequilibrium between zone-center optical phonons and other modes

Nonequilibrium ratio increases with smaller laser spots and substrate effects

Abstract

Previous multitemperature model (MTM) resolving phonon temperatures at the polarization level and measurements have uncovered remarkable nonequilibrium among different phonon polarizations in laser irradiated graphene and metals. Here, we develop a semiconductor-specific MTM (SC-MTM) by including electron-hole pair generation, diffusion, and recombination, and show that a phonon polarization-level model does not yield observable polarization-based nonequilibrium in laser-irradiated molybdenum disulfide (MoS$_2$). In contrast, appreciable nonequilibrium is predicted between zone-center optical phonons and the other modes. The momentum-based nonequilibrium ratio is found to increase with decreasing laser spot size and interaction with a substrate. This finding is relevant to the understanding of the energy relaxation process in two-dimensional optoelectronic devices and Raman measurements of thermal transport.