Transfer-matrix approach to multiband Josephson junctions

TL;DR

This paper develops a transfer-matrix formalism for multiband Josephson junctions, specifically applied to MgB2, revealing how interband tunneling influences critical current and conductance with varying electrode orientation.

Contribution

It introduces a generalized transfer-matrix approach for multiband superconductors and models interband tunneling effects based on misorientation angles.

Findings

Interband tunneling increases with misorientation angle.

Features in conductance spectra are affected by interband processes.

Critical current depends on junction orientation and transparency.

Abstract

We study the influence of multiple bands on the properties of Josephson junctions. In particular we focus on the two gap superconductor magnesium diboride. We present a formalism to describe tunneling at a point contact between two MgB2 electrodes generalizing the transfer-matrix approach to multiple bands. A simple model is presented to determine the effective hopping amplitudes between the different energy bands as a function of the misorientation angle of the electrodes. We calculate the critical current and the current-voltage characteristics for N-I-S and S-I-S contacts with different orientation for junctions with both high and low transparency. We find that interband tunneling processes become increasingly important with increasing misorientation angle. This is reflected in certain features in the differential tunneling conductance in both the tunneling limit as well as for multiple Andreev reflections.