Quasiclassical theory of twin boundaries in High-T_c superconductors

TL;DR

This paper uses quasiclassical theory to study twin boundaries in high-T_c superconductors, revealing a spontaneous current and time-reversal symmetry breaking that can be detected by STM.

Contribution

It introduces a microscopic model showing spontaneous currents and symmetry breaking at twin boundaries in high-T_c materials.

Findings

Spontaneous currents arise at twin boundaries at low temperatures.

Zero-bias peak splits due to time-reversal symmetry breaking.

Splitting is detectable by STM as a signature of the new state.

Abstract

We investigate the electronic structure of twin boundaries in orthorhombically distorted high-T$_c$ materials using the quasiclassical theory of superconductivity. At low temperatures we find a local instability to a time-reversal symmetry breaking state at the twin boundary. This state yields spontaneous currents along the twin boundary that are microscopically explained by the structure of the quasiparticle bound states. We calculate the local density of states and find a splitting in the zero-bias peak once the spontaneous currents set in. This splitting is measurable by STM techniques and is a unique signature of time-reversal breaking states at a twin boundary.