Non-Fermi-liquid states and pairing instability of a general model of copper oxide metals

Abstract

A model of copper-oxygen bonding and anti-bonding bands with the most general two-body interactions allowable by symmetry is considered. The model has a continuous transition as a function of hole-density x and temperature T to a phase in which a current circulates in each unit cell. This phase preserves the translational symmetry of the lattice while breaking time-reversal invariance and the four-fold rotational symmetry. The product of time-reversal and four-fold rotation is preserved. The circulating current phase terminates at a critical point at x = x c , T = 0. In the quantum-critical region about this point the logarithm of the frequency of the current fluctuations scales with their momentum. The microscopic basis for the marginal Fermi-liquid phenemenology and the observed long wavelength transport anomalies near x = x c are derived from such fluctuations. The symmetry of the current fluctuations is such that the associated magnetic field fluctuations are absent at oxygen sites and have the correct form to explain the anomalous copper nuclear relaxation rate. Cross-overs to the Fermi-liquid phase on either side of x c and the role of disorder are briefly considered. The current fluctuations promote superconductive instability with a propensity towards "D-wave" symmetry or "extended S-wave"symmetry depending on details of the band-structure. Several experiments are proposed to test the theory.

Staggered Flux State in Two-Dimensional Hubbard Models

“…120 The above neutron experiments appear to be consistent with more complicated circular-current states that do not break this symmetry. 90,121,122 Recently, however, one of the authors showed that this type of circular-current state is not stabilized with respect to the normal state in a wide range of the model parameters on the basis of systematic VMC calculations with refined wave functions for d-p-type models. Instead, SF states are stabilized in some parameter ranges.…”

Singular or non-Fermi liquids

“…(a) Diagram for the singular contribution to the one-particle self-energy with the uctuating (q; ). g's are the vertices which in microscopic theory [270] is shown to have important momentum dependence, but which gives negligible momentum dependence to the self-energy. (b) For 0 (q; ) which is momentum independent, a total vertex may sometimes be usefully deÿned, which has the same frequency dependence as Eq.…”

Energy gaps in the failed high-Tc superconductor La1.875Ba0.125CuO4

“…As suggested by its different momentum dependence from its nodal counterpart, the antinodal pseudogap may have a different origin, which has been the subject for intense discussions in the literature [2][3][4][5][6][7][8][9] . Generally, as inferred from Supplementary Information, Fig.…”