Magnetic impurities in a superconductor: Effect of domain walls and interference

TL;DR

This paper investigates how magnetic impurities arranged in domain walls affect quasiparticle behavior, local density of states, and induce quantum phase transitions in a superconductor, highlighting complex interference effects.

Contribution

It introduces a study of regularly arranged magnetic impurities forming domain walls in superconductors, exploring their impact on quasiparticles and phase transitions, which is a novel approach compared to previous disordered models.

Findings

Impurities cause complex interference phenomena in quasiparticle wave functions.

Magnetic impurities induce quantum phase transitions in the superconductor.

Regularly arranged impurities in domain walls influence local density of states.

Abstract

We consider the effect of magnetic impurities, modeled by classical spins, in a conventional superconductor. We study their effect on the quasiparticles, specifically on the spin density and local density of states (LDOS). As previously emphasized, the impurities induce multiple scatterings of the quasiparticle wave functions leading to complex interference phenomena. Also, the impurities induce quantum phase transitions in the many-body system. Previous authors studied the effect of either a small number of impurities (from one to three) or a finite concentration of impurities, typically in a disordered distribution. In this work we assume a regular set of spins distributed inside the superconductor in such a way that the spins are oriented, forming different types of domain walls, assumed stable. This situation may be particularly interesting in the context of spin transfer due to polarized currents traversing the material.