Ab-initio density-matrix approach to exciton coherence: phonon scattering, Coulomb interactions and radiative recombination

TL;DR

This paper introduces an ab initio density-matrix approach to model exciton relaxation in semiconductors, accounting for phonon, Coulomb, and radiative processes, providing detailed insights into excited-state dynamics in materials like TMDs.

Contribution

The work extends a Lindblad density-matrix formalism to include multi-channel relaxation processes, enabling first-principles study of exciton dynamics in realistic materials.

Findings

Demonstrated the method on monolayer MoSe2

Analyzed effects of many-body interactions on exciton dynamics

Provided detailed relaxation pathways and spectral signatures

Abstract

Relaxation processes following light excitation in semiconductors are key in materials-based quantum technology applications. These processes are broadly studied in atomically thin transition metal dichalcogenides (TMDs), quasi-two-dimensional excitonic semiconductors in which atomistic design allows for tunable excited-state properties, such as relaxation lifetimes and photo-induced coherence. In this work, we present a density-matrix-based approach to compute exciton relaxation within a many-body ab initio perspective. We expand our previously developed Lindblad density-matrix formalism to capture multi-channel electron-hole pair relaxation processes, including phonon and Coulomb scattering as well as radiative recombination, and study their effect on the time-resolved excited-state propagation. Using monolayer MoSe$_2$ as a prototypical example, we examine many-body effects on the time-dependent dynamics of photoactive excitations, exploring how the electron-hole pair interactions are reflected in variations of the excitation energy, spectral signature, and state coherence. Our method supplies a detailed understanding of exciton relaxation mechanisms in realistic materials, offering a previously unexplored pathway to study excited-state dynamics in semiconductors from first principles.