Numerical analysis of three-band models for CuO planes as candidates for a spontaneous T violating orbital current phase

TL;DR

This study numerically investigates three-band models for CuO planes in high-Tc superconductors, finding no evidence for proposed time-reversal symmetry violating current patterns and constraining their energy scale.

Contribution

The paper provides a detailed numerical analysis of current-current correlations in three-band models, extending previous work and setting limits on the energy of potential loop currents.

Findings

No evidence for the proposed current patterns.

Loop current energy must be less than 5 meV per link.

Weak dependence on inter-atomic Coulomb repulsion.

Abstract

Recently, we have numerically evaluated the current-current correlation function for the ground states of three-band models for the CuO planes of high-Tc superconductors at hole doping x=1/8 using systems with 24 sites and periodic boundary conditions. In this article, the numerical analysis is explicated in detail and extended to a wider range of parameters. Our results show no evidence for the time-reversal symmetry violating current patterns recently proposed by Varma. If such current patterns exist, our results indicate that the energy associated with the loop currents must be smaller than 5 meV per link even if the on-site chemical potential on the oxygen sites, which is generally assumed to be of the order of 3.6 eV, is taken to zero, as advocated by Varma. We also vary the inter-atomic Coulomb repulsion scale and find only a weak dependence on this parameter. So while our studies do not rule out the existence of such current patterns, they do rule out that quantum critical fluctuations of these patterns are responsible for phenomena occurring at significantly higher energies such as the superconductivity or the anomalous properties observed in the strange metal phase provided the CuO superconductors are adequately described by any of the three-band models discussed.