Nonlocal correlations in the optical conductivity spectra

Dobushovskyi Dobushovskyi,Shvaika Shvaika

doi:10.5488/cmp.21.23702

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.

Highlights

Electron correlations attract a great interest in connection with various phenomena in different materials, from the one- and two-dimensional organic conductors, through three-dimensional solids, up to the optical lattices
The density of states (DOS) is smooth at the Fermi level [figure 1(a)] and both the current-current correlation function χ(Ω) and optical conductivity σ(Ω) display Drude peak at low frequencies, see figure 2
In this article we studied an influence of correlated hopping on the optical spectra for the FalicovKimball model on a Bethe lattice with a semielliptic DOS

Summary

Introduction

Electron correlations attract a great interest in connection with various phenomena in different materials, from the one- and two-dimensional organic conductors, through three-dimensional solids, up to the optical lattices As it was noticed by Hubbard in his seminal article [1], the second quantized representation of the inter-electron Coulomb interaction should take into account, besides the local term U i ni↑ni↓, the nonlocal contributions including the inter-site Coulomb interaction ij Vij ninj and the so-called correlated hopping ti(2j )(niσ + njσ )ci†σ cjσ, ijσ (1.1). We study the effects of correlated hopping using the Falicov-Kimball model [18], the simplest model of strongly correlated electrons, which considers the local interaction between the itinerant d electrons and localized f electrons It is a binary alloy type model and its ground state phase diagram for the one-dimensional (D = 1) and two-dimensional (D = 2) cases displays a variety of modulated.

The model Hamiltonian

The single particle Green’s function

Optical conductivity in the presence of correlated hopping

Results and discussion

Conclusions