An SU(2) Formulation of the t-J model: Application to Underdoped Cuprates

TL;DR

This paper introduces an SU(2) symmetric slave-boson approach to the t-J model, capturing key phases of cuprate superconductors and revealing new low-energy modes, thus advancing understanding of high-temperature superconductivity.

Contribution

It develops a novel SU(2) slave-boson formulation of the t-J model that captures multiple phases and introduces new low-energy fluctuation modes.

Findings

Reproduces cuprate phase diagram including d-wave superconductivity and pseudogap phases.

Shows evolution of Fermi surface from small segments to large surface with doping.

Identifies new low-energy modes overlooked in previous U(1) theories.

Abstract

We develop a slave-boson theory for the t-J model at finite doping which respect a SU(2) symmetry -- a symmetry previously known to be important at half filling. The mean field phase diagram is found to be consistent with the phases observed in the cuprate superconductors, which contains d-wave superconductor, spin gap, strange metal, and Fermi liquid phases. The spin gap phase is best understood as the staggered flux phase, which is nevertheless translationally invariant for physical quantities. The physical electron spectral function shows small Fermi segments at low doping which continuously evolve into the large Fermi surface at high doping concentrations. The close relation between the SU(2) and the U(1) slave-boson theory is discussed. The low energy effective theory for the low lying fluctuations is derived, and new lying modes (which were over looked in the U(1) theory) are identified.