Circuit theory of unconventional superconductor junctions

TL;DR

This paper extends superconducting circuit theory to include unconventional superconductor junctions, accounting for zero-energy Andreev bound states and analyzing their impact on transport and proximity effects.

Contribution

It introduces a generalized circuit theory framework for unconventional superconductor junctions, capturing zero-energy bound states and their influence on mesoscopic transport.

Findings

Zero-energy Andreev bound states significantly affect transport properties.

The orientation of the junction interface influences the competition between bound states and proximity effect.

The extended theory accurately describes transport in systems with unconventional superconductors.

Abstract

We extend the circuit theory of superconductivity to cover transport and proximity effect in mesoscopic systems that contain unconventional superconductor junctions. The approach fully accounts for zero-energy Andreev bound states forming at the surface of unconventional superconductors. As a simple application, we investigate the transport properties of a diffusive normal metal in series with a d-wave superconductor junction. We reveal the competition between the formation of Andreev bound states and proximity effect, that depends on the crystal orientation of the junction interface.