An ab-initio approach to describe coherent and non-coherent exciton dynamics

TL;DR

This paper presents an ab initio method using non-equilibrium many-body perturbation theory to describe both coherent and non-coherent exciton dynamics in materials subjected to ultra-short laser pulses.

Contribution

It introduces a theoretical framework that extends NEQ-MBPT to accurately model exciton dynamics, including electron-hole binding effects, in a low-density regime.

Findings

Provides a unified description of exciton dynamics.

Applicable for ab initio simulations of ultrafast processes.

Bridges the gap between coherent and non-coherent regimes.

Abstract

The use of ultra-short laser pulses to pump and probe materials activates a wealth of processes which involve the coherent and non coherent dynamics of interacting electrons out of equilibrium. Non equilibrium (NEQ) many body perturbation theory (MBPT) offers an equation of motion for the density-matrix of the system which well describes both coherent and non coherent processes. In the non correlated case there is a clear relation between these two regimes and the matrix elements of the density-matrix. The same is not true for the correlated case, where the potential binding of electrons and holes in excitonic states need to be considered. In the present work we discuss how NEQ-MBPT can be used to describe the dynamics of both coherent and non-coherent excitons in the low density regime. The approach presented is well suited for an ab initio implementation.