SO(6)-Generalized Pseudogap Model of the Cuprates

TL;DR

This paper presents an SO(6)-based theoretical framework to describe the pseudogap and superconducting phases in cuprates, emphasizing competing instabilities and extending previous models to include various order parameters.

Contribution

It introduces SO(6) generalizations of the pBF model, incorporating flux phase and d-wave superconductivity, to better understand the pseudogap phenomena in cuprates.

Findings

The pseudogap is linked to competing nesting instabilities, not superconductivity.

The SO(6) model captures the phase diagram and spectral features of cuprates.

Experimental evidence suggests a non-superconducting component to the pseudogap.

Abstract

The smooth evolution of the tunneling gap of Bi_2Sr_2CaCu_2O_8 with doping from a pseudogap state in the underdoped cuprates to a superconducting state at optimal and overdoping reflects an underlying SO(6) instability structure of the (pi,0) saddle points. The pseudogap is probably not associated with superconductivity, but is related to competing nesting instabilities, which are responsible for the stripe phases. We earlier introduced a simple Ansatz of this competition in terms of a pinned Balseiro-Falicov (pBF) model of competing charge density wave and (s-wave) superconductivity. This model gives a good description of the phase diagram and the tunneling and photoemission spectra. Here, we briefly review these results, and discuss some recent developments: experimental evidence for a non-superconducting component to the pseudogap; and SO(6) generalizations of the pBF model, including flux phase and d-wave superconductivity.