Influence Functional Approach to Non-Perturbative Exciton Binding Renormalization from Phonons

TL;DR

This paper develops a first-principles many-body model to non-perturbatively analyze how phonons influence exciton binding energies across temperatures, revealing significant effects from optical phonons.

Contribution

It introduces a novel influence functional approach combined with path integral Monte Carlo to accurately compute temperature-dependent exciton binding energies from first principles.

Findings

Exciton binding energies agree with experimental data for Wannier-Mott excitons.

Optical phonons significantly renormalize exciton binding energies at higher temperatures.

Long-range and short-range phonon interactions both impact polaron and exciton properties.

Abstract

We construct a many-body model Hamiltonian to capture how phonons renormalize exciton binding as a function of temperature. By using the GW approximation and density functional perturbation theory, we are able to parameterize this Hamiltonian completely from first principles. To capture static quasiparticle properties non-perturbatively, we evolve this Hamiltonian in imaginary time with path integral Monte Carlo using an influence functional based approach. For a class of Wannier-Mott type excitons, our binding energies are in quantitative agreement with experiment. We find that in addition to long-range dipolar interactions from longitudinal optical modes, short-ranged deformation potentials from acoustic modes and transverse optical modes can significantly renormalize electron and hole polaron binding energies at elevated temperature. However, exciton binding energies are only appreciably renormalized by coupling to optical phonons.