Triplet superconductivity and proximity effect induced by Bloch and N\'{e}el domain walls

TL;DR

This study investigates how Bloch and Néel domain walls in superconductor/ferromagnet heterostructures induce spin-triplet pairing correlations, revealing that Bloch walls uniquely generate strong equal-spin correlations, advancing understanding of long-range proximity effects.

Contribution

It provides a self-consistent theoretical analysis of Bloch and Néel domain walls' effects on triplet pairing, highlighting conditions for equal-spin correlations in heterostructures.

Findings

Both domain walls generate similar triplet correlations as conical layers.

Only Bloch domain walls produce strong equal-spin correlations in the studied geometries.

Néel domain walls induce equal-spin correlations only when oriented within the interface plane.

Abstract

Noncollinear magnetic interfaces introduced in superconductor (SC)/ferromagnet/SC heterostructures allow for spin-flipping processes and are able to generate equal-spin spin-triplet pairing correlations within the ferromagnetic region. This leads to the occurrence of the so-called long-range proximity effect. Particular examples of noncollinear magnetic interfaces include Bloch and N\'{e}el domain walls. Here, we present results for heterostructures containing Bloch and N\'{e}el domain walls based on self-consistent solutions of the spin-dependent Bogoliubov$-$de Gennes equations in the clean limit. In particular, we investigate the thickness dependence of Bloch and N\'{e}el domain walls on induced spin-triplet pairing correlations and compare with other experimental and theoretical results, including conical magnetic layers as noncollinear magnetic interfaces. It is shown that both, Bloch and N\'{e}el domain walls lead to the generation of unequal-spin spin-triplet pairing correlations of similar strength as for conical magnetic layers. However, for the particular heterostructure geometries investigated, only Bloch domain walls lead to the generation of equal-spin spin-triplet pairing correlations. They are stronger than those generated by an equivalent thickness of conical magnetic layers. In order for N\'{e}el domain walls to induce equal-spin spin-triplet pairing correlations, they have to be oriented such that the noncollinearity appears within the plane parallel to the interface region.