Properties of the zero energy Andreev bound state in a two sublattice SNS junction

TL;DR

This paper investigates how inter-sublattice pairing affects zero energy Andreev bound states in a two-sublattice SNS junction, revealing phase-dependent stability of zero bias peaks relevant to iron-based superconductors.

Contribution

It introduces a model with intra- and inter-sublattice pairing in SNS junctions and analyzes their impact on zero bias peaks, connecting to odd parity pairing in FeSCs.

Findings

Zero bias peak stability depends on phase difference across sublattices.

Inter-sublattice pairing destabilizes ZBP at phase difference of π.

Results relate to odd parity -η pairing in iron-based superconductors.

Abstract

We study properties of the zero energy Andreev bound state in a superconductor-normal metal-superconductor(SNS) junction consisting of two intrinsic degrees of freedom. The superconductors on either sides of the normal metal are assumed to have two sublattices with an $intra$-sublattice pairing with a phase of zero or $\pi$ between the two sublattices. In addition, we add a uniform $inter$-sublattice pairing and study its effect on the local density of states (LDOS). In particular, we find that as the inter-sublattice pairing is turned on, the zero bias peak (ZBP) is unstable (robust) when the phase difference across the sublattices is $\pi$ (zero). We discuss the relevance of our results to the recently proposed odd parity $-\eta$ pairing ground states in Iron based superconductors (FeSCs).