Time-reversal symmetry breaking surface states in t-J model

TL;DR

This paper derives a Ginzburg-Landau free energy microscopically from the t-J model to explain time-reversal symmetry breaking surface states observed near Josephson junctions in high-temperature superconductors.

Contribution

It provides a microscopic derivation of a phenomenological GL theory for T-breaking surface states in the t-J model, linking theory to experimental observations.

Findings

GL free energy satisfies conditions for T-violating surface states

Microscopic derivation supports phenomenological models

Potential explanation for experimental T-breaking phenomena

Abstract

Recently a phenomenological Ginzburg-Landau (GL) theory has been proposed to describe the occurrence of a locally time-reversal symmetry (T) breaking state near a Josephson junction between unconventional superconductors. In this paper we derive this type of GL free energy microscopically from the t-J model within a slave-boson mean-field approximation. The resulting GL free energy is shown to satisfy the conditions to have a T-violating surface state. The existence of this junction state may explain some of the recent experiments on High-Tc superconductors.