Nonlocal correlations in the optical conductivity spectra

TL;DR

This paper investigates how correlated hopping affects the optical conductivity spectra in the Falicov-Kimball model, revealing complex spectral features and the influence of strong correlations on the Drude peak and density of states.

Contribution

It derives an expression for the current-current correlation function within dynamical mean field theory for the model with correlated hopping, highlighting spectral shape changes.

Findings

Deviations from Debye relaxation in the Drude peak for small correlated hopping.

Emergence of additional peaks in optical spectra near the two-particle resonance.

Reduction of the upper Hubbard band width and Drude spectral weight at strong correlations.

Abstract

Optical conductivity spectra are studied for the Falicov-Kimball model with correlated hopping on the Bethe lattice. An expression for the current-current correlation function is derived using dynamical mean field theory. In the metallic phase with small correlated hopping values, the shape of Drude peak deviates from the Debye relaxation peak, and an additional wide peak is observed on the optical conductivity spectra and on Nyquist plot when Fermi level is in the vicinity of the two particle resonance. At larger values of the correlated hopping parameter, the density of states contains three bands and the corresponding optical spectra and Nyquist plots display a more complicated shape with additional peaks. For strong local correlations, the correlated hopping reduces the width of the upper Hubbard band resulting in a decrease of the Drude peak spectral weight for the doped Mott insulator.