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Journal of Physics Condensed Matter

Dynamical mean field theory study of a simplified model for CuO2planes

Anderson Beatrici, M. A. Gusmão

Published Dec 2, 2005• 1 citation
Publisher

Abstract

Following previous work on Hubbard and Anderson models, we introduce a simplified three-band Hubbard model for CuO2 planes of high-Tc superconductors. This allows for exact evaluation of single-particle Green's functions within the dynamical mean field approach. Keeping information about the lattice structure through the appropriate bare density of states, we study the existence of magnetic solutions, and their stability with respect to variations of the doping fraction, interaction parameters, and temperature. Normal-state properties of known superconducting cuprates are reproduced, and we show that the model has room for substantial enhancement of N?el temperatures.

DOI
10.1088/0953-8984/17/50/025

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We present an exact formulation of the single-particle Green's functions for the two-dimensional three-band Hubbard model of the CuO2{\mathrm{CuO}}_{2}CuO2​ lattice based on a projection-operator formalism of Mori. The model is general and incorporates the various known local-density-approximation (LDA) interaction parameters. In this paper we present only the mean-field results. The inclusion of self-energy effects will be presented elsewhere. Already, in the mean-field approximation, we find that properties such as hole occupations and magnetic moments compare remarkably well with those from quantum Monte Carlo (MC) calculations. The densities of states are also calculated for various hole dopings, again using the parameters from the LDA calculations. Finally the detailed effect of hopping between different O p orbitals, are also presented.
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Abstract The nature of the effective interaction responsible for pairing in the high-temperature superconducting cuprates remains unsettled. This question has been studied extensively using the simplified single-band Hubbard model, which does not explicitly consider the orbital degrees of freedom of the relevant CuO2 planes. Here, we use a dynamical cluster quantum Monte Carlo approximation to study the orbital structure of the pairing interaction in the three-band Hubbard model, which treats the orbital degrees of freedom explicitly. We find that the interaction predominately acts between neighboring copper orbitals, but with significant additional weight appearing on the surrounding bonding molecular oxygen orbitals. By explicitly comparing these results to those from the simpler single-band Hubbard model, our study provides strong support for the single-band framework for describing superconductivity in the cuprates.