Physics of the Pseudogap in 8-site Cluster Dynamical Mean Field Theory: photoemission, Raman scattering, in-plane and c-axis conductivity

TL;DR

This study uses an 8-site cluster dynamical mean field approach to explore the pseudogap phenomenon in the Hubbard model, revealing how it varies with doping and temperature, and aligning with high-$T_c$ cuprate observations.

Contribution

It provides detailed theoretical estimates of spectral and conductivity properties in the Hubbard model, highlighting the pseudogap's doping and temperature dependence using an 8-site cluster approximation.

Findings

Pseudogap appears near half filling and decreases with doping.

Pseudogap fills in with increasing temperature, rather than closing.

Calculated response functions resemble experimental data in high-$T_c$ cuprates.

Abstract

Cluster dynamical mean field and maximum entropy analytical continuation methods are used to obtain theoretical estimates for the many-body density of states, electron self-energy, in-plane and c-axis optical conductivity and the $B_{1g}$ and $B_{2g}$ Raman scattering spectra of the two dimensional square lattice Hubbard model at intermediate interaction strengths and carrier concentrations near half filling. The calculations are based on an 8-site cluster approximation which gives access to both the zone-diagonal and zone-face portions of the Fermi surface. At low dopings the zone-face regions exhibit a 'pseudogap', a suppression of the many-body density of states for energies near the Fermi surface. The pseudogap magnitude is largest near half filling and decreases smoothly with doping, but as temperature is increased the gap fills in rather than closes. The calculated response functions bear a strong qualitative resemblance to data taken in the pseudogap regime of high-$T_c$ cuprates, strongly suggesting that the intermediate coupling Hubbard model accounts for much of the exotic behavior observed in high-$T_c$ materials.