Bound states at the interface between antiferromagnets and superconductors

TL;DR

This paper provides a comprehensive theoretical analysis of interfaces between itinerant antiferromagnets and superconductors, revealing how quasiparticle states and local density of states are affected by interface properties and misorientation angles.

Contribution

It introduces a detailed numerical and analytical study of quasiparticle states at AF-superconductor interfaces, including effects of pair breaking and interface potentials.

Findings

Strong pair-breaking effects at AF/sSC interfaces due to low-energy Andreev states

Potential barriers create additional extrema in quasiparticle spectra

Quasiparticle levels in AF-normal metal systems depend on magnetization misorientation

Abstract

We present a detailed theoretical investigation of interfaces and junctions involving itinerant antiferromagnets. By solving the Bogoliubov-de Gennes equations with a tight-binding model on a square lattice, we study both the self-consistent order parameter fields proximate to interfaces between antiferromagnets (AF) and s-wave (sSC) or d-wave (dSC) superconductors, the dispersion of quasiparticle subgap states at interfaces and interlayers, and the local density of states (LDOS) as a function of distance from the interface. In addition, we present the quasiclassical approach to interfaces and junctions involving itinerant antiferromagnets developed in an earlier paper. Analytical results are in excellent agreement with what we obtain numerically. Strong effects of pair breaking in the presence of low-energy interface Andreev states are found in particular for AF/sSC interfaces when interface potentials are not too high. Potential barriers induce additional extrema in the dispersive quasiparticle spectra with corresponding peaks in the LDOS. Discrete quasiparticle dispersive levels in AF - normal metal (N) - AF systems are found to strongly depend on the misorientation angle of the magnetizations in the two antiferromagnets.