A Theory of the Pseudogap State of the Cuprates

TL;DR

This paper proposes a theoretical model for the pseudogap phase in cuprates, predicting a time-reversal violating state with an anisotropic gap that matches experimental observations and suggests new avenues for experimental verification.

Contribution

It introduces a mean-field model for cuprates that explains the pseudogap phase as a time-reversal violating state with specific spectral properties.

Findings

The model predicts a phase with zero density of states at certain points, consistent with the pseudogap.

Calculated temperature-dependent spectra match experimental data.

The phase ends at a quantum critical point as doping varies.

Abstract

The phase diagram for a general model for Cuprates is derived in a mean-field approximation. A phase violating time-reversal without breaking translational symmetry is possible when both the ionic interactions and the local repulsions are large compared to the energy difference between the Cu and O single-particle levels. It ends at a quantum critical point as the hole or electron doping is increased. Such a phase is necessarily accompanied by singular forward scattering such that, in the stable phase, the density of states at the chemical potential, projected to a particular point group symmetry of the lattice is zero producing thereby an anisotropic gap in the single-particle spectrum. It is suggested that this phase occupies the "pseudogap" region of the phase diagram of the cuprates. The temperature dependence of the single-particle spectra, the density of states, the specific heat and the magnetic susceptibility are calculated with rather remarkable correspondence with the experimental results. The importance of further direct experimental verification of such a phase in resolving the principal issues in the theory of the Cuprate phenomena is pointed out. To this end, some predictions are provided.