Modelling excitonic Mott transitions in two-dimensional semiconductors

TL;DR

This paper models the optical properties of two-dimensional semiconductors, focusing on excitonic Mott transitions, by developing a microscopic approach that includes many-particle correlations and can handle regimes with high Fermi energies.

Contribution

It introduces a novel microscopic modeling method that incorporates many-particle correlations to accurately describe excitonic Mott transitions in 2D semiconductors.

Findings

Model captures the emergence of trion-like peaks in absorption spectra.

Approach allows for rigorous modeling near the excitonic Mott transition.

Enables analysis of optical responses when Fermi energies are comparable to binding energies.

Abstract

We analyze the many-particle correlations that affect the optical properties of two-dimensional semiconductors. These correlations manifest themselves through the specific optical resonances such as excitons, trions, etc. Starting from the generic electron-hole Hamiltonian and employing the microscopic Heisenberg equation of motion the infinite hierarchy of differential equations can be obtained. In order to decouple the system we address the cluster expansion technique which provides a regular procedure of consistent accounting of many-particle correlation contributions into the interband polarization dynamics. In particular, the partially taken into account three-particle correlations modify the behavior of absorption spectra with the emergence of a trion-like peak additional to excitonic ones. In contrast to many other approaches, the proposed one allows us to model the optical response of 2d semiconductors in the regime when the Fermi energies are of the order of the exciton and trion binding energies, thus allowing us to rigorously model the onset of the excitonic Mott transition, the regime being recently studied in various 2d semiconductors, such as transition metal dichalcogenides.