Dynamical Exchange Effects in a Two-Dimensional Many-Polaron Gas

TL;DR

This paper investigates how dynamical exchange effects influence the response and static properties of a two-dimensional many-polaron gas, revealing significant corrections to common approximation methods and improving understanding of optical and energetic behaviors.

Contribution

It introduces a dielectric function derived from time-dependent Hartree-Fock formalism to account for dynamical exchange effects in many-polaron systems, surpassing the random-phase approximation.

Findings

Dynamical exchange effects cause substantial corrections to ground state energy, effective mass, and optical conductivity.

The reduction of optical spectral weight above phonon frequency is overestimated by RPA.

The new approach provides more accurate descriptions of many-polaron system properties.

Abstract

We calculate the influence of dynamical exchange effects on the response properties and the static properties of a two-dimensional many-polaron gas. These effects are not manifested in the random-phase approximation which is widely used in the analysis of the many-polaron system. Here they are taken into account by using a dielectric function derived in the time-dependent Hartree-Fock formalism. At weak electron-phonon coupling, we find that dynamical exchange effects lead to substantial corrections to the random-phase approximation results for the ground state energy, the effective mass, and the optical conductivity of the polaron system. Furthermore, we show that the reduction of the spectral weight of the optical absorption spectrum at frequencies above the longitudinal optical phonon frequency, due to many-body effects, is overestimated by the random-phase approximation.