Proximity Effect and Josephson Coupling in the SO(5) Theory of High-Tc Superconductivity

TL;DR

This paper explores the proximity effect and Josephson coupling in high-Tc superconductors using the SO(5) theory, revealing how junction thickness influences the transition between superconducting and antiferromagnetic states.

Contribution

It introduces a model for S-A-S junctions based on SO(5) theory, predicting a critical thickness for phase transitions and unique current-phase relations.

Findings

Narrow junctions behave like strong superconductors.

Critical junction thickness depends on SO(5) coupling and phase difference.

Thin junctions exhibit a sharp change in current-phase relation.

Abstract

We consider proximity effect coupling in Superconducting/Antiferromagnetic/Superconducting (S-A-S) sandwiches using the recently developed SO(5) effective theory of high temperature superconductivity. We find that, for narrow junctions, the A region acts like a strong superconductor, and that there is a critical junction thickness which depends on the effective SO(5) coupling constants and on the phase difference across the junction, at which the A region undergoes a Freedericksz-like transition to a state which is intermediate between superconductor and antiferromagnet. For thick junctions, the current-phase relation is sinusoidal, as in standard S-N-S and S-I-S junctions, but for thin junctions it shows a sharp break in slope at the Freedericksz point.