Polaronic features in the optical properties of the Holstein-t-J model

TL;DR

This paper provides an exact DMFT solution for the optical conductivity of a hole in the Holstein-t-J model, revealing how polaron formation affects optical features and pseudogap behavior.

Contribution

It introduces an exact analytical solution for optical conductivity in the Holstein-t-J model, linking spectral features to polaronic and magnetic excitations.

Findings

Identification of two mechanisms for pseudogap filling and closing.

Coexistence of magnon peak and broad polaronic band in optical absorption.

Analytical expression for optical conductivity in the polaronic regime.

Abstract

We derive the exact solution for the optical conductivity $\sigma(\omega)$ of one hole in the Holstein-t-J model in the framework of dynamical mean-field theory (DMFT). We investigate the magnetic and phonon features associated with polaron formation as a function of the exchange coupling $J$, of the electron-phonon interaction $\lambda$ and of the temperature. Our solution directly relates the features of the optical conductivity to the excitations in the single-particle spectral function, revealing two distinct mechanisms of closing and filling of the optical pseudogap that take place upon varying the microscopic parameters. We show that the optical absorption at the polaron crossover is characterized by a coexistence of a magnon peak at low frequency and a broad polaronic band at higher frequency. An analytical expression for $\sigma(\omega)$ valid in the polaronic regime is presented.