Pseudogaps in Strongly Correlated Metals: Optical Conductivity within the Generalized Dynamical Mean-Field Theory Approach

TL;DR

This paper uses an advanced dynamical mean-field theory approach to study optical conductivity in doped Hubbard models, revealing pseudogap phenomena similar to those observed in copper oxide superconductors.

Contribution

It introduces a generalized DMFT approach incorporating non-local correlations via a momentum-dependent self-energy, providing new insights into pseudogap behavior in strongly correlated metals.

Findings

Pseudogap behavior observed in optical conductivity matches experimental data.

Large U suppresses pseudogap anomalies.

Method captures short-range spin fluctuation effects.

Abstract

Optical conductivity of the weakly doped two-dimensional repulsive Hubbard model on the square lattice with nearest and next nearest hoppings is calculated within the generalized dynamical-mean field (DMFT+\Sigma_p) approach which includes correlation length scale \xi into the standard DMFT equations via the momentum dependent self-energy \Sigma_p, with full account of appropriate vertex corrections. This approach takes into consideration non-local dynamical correlations induced e.g. by short-ranged collective SDW-like antiferromagnetic spin fluctuations, which (at high enough temperatures) can be viewed as a quenched Gaussian random field with finite correlation length \xi. The effective single impurity problem is solved by numerical renormalization group (NRG). We consider both the case of correlated metal with the bandwidth W<=U and that of doped Mott insulator with U>>W (U - value of local Hubbard interaction). Optical conductivity calculated within DMFT+\Sigma_p demonstrates typical pseudogap behavior within the quasiparticle band in qualitative agreement with experiments in copper oxide superconductors. For large values of U pseudogap anomalies are effectively suppressed.