Renormalization of excitonic properties by polar phonons

TL;DR

This paper uses path integral molecular dynamics to analyze how electron-phonon interactions influence excitonic properties in semiconductors, revealing phonon-induced screening effects that modify exciton binding energies and lifetimes.

Contribution

It introduces a nonperturbative path integral approach to evaluate excitonic property renormalization due to phonons, including mass, binding energy, and recombination rates.

Findings

Phonons screen electron-hole interactions, reducing exciton binding energies.

Phonons increase exciton radiative lifetimes.

The approach aligns qualitatively with perturbative and variational methods.

Abstract

We employ quasiparticle path integral molecular dynamics to study how the excitonic properties of model semiconductors are altered by electron-phonon coupling. We describe ways within a path integral representation of the system to evaluate the renormalized mass, binding energy, and radiative recombination rate of excitons in the presence of a fluctuating lattice. To illustrate this approach, we consider Fr\"ohlich-type electron-phonon interactions and employ an imaginary time influence functional to incorporate phonon-induced effects nonperturbatively. The effective mass and binding energies are compared with perturbative and variational approaches, which provide qualitatively consistent trends. We evaluate electron-hole recombination rates as mediated through both trap-assisted and bimolecular processes, developing a consistent statistical mechanical approach valid in the reaction limited regime. These calculations demonstrate how phonons screen electron-hole interactions, generically reducing exciton binding energies and increasing their radiative lifetimes.