Transport in multi-terminal superconductor/ferromagnet junctions having spin-dependent interfaces

TL;DR

This paper investigates electronic transport in superconductor/ferromagnet junctions with spin-dependent interfaces, revealing complex behaviors like enhanced crossed Andreev reflection and resistance sign changes, aligning with experimental observations.

Contribution

It introduces an extended Blonder-Tinkham-Klapwijk model incorporating spin-dependent interfacial barriers to explain transport phenomena in superconductor/ferromagnet junctions.

Findings

Enhanced crossed Andreev reflection due to spin-dependent scattering.

Sign change in resistance depending on magnetization alignment.

Model explains both positive and negative resistance experimental results.

Abstract

We study electronic transport in junctions consisting of a superconductor electrode and two ferromagnet (F) leads in which crossed Andreev reflections (CAR) and elastic cotunnelings are accommodated. We model the system using an extended Blonder-Tinkham-Klapwijk treatment with a key modification that accounts for spin-dependent interfacial barriers (SDIB). We compute current-voltage relations as a function of parameters characterizing the SDIB, magnetization in the F leads, geometry of the junction, and temperature. Our results reveal a rich range of significantly altered physics due to a combination of interfering spin-dependent scattering processes and population imbalance in the ferromagnets, such as a significant enhancement in CAR current and a sign change in the relative difference between resistance of two cases having a antiparallel or parallel alignment of the magnetization in the F leads, respectively. Our model accounts for the surprising experimental findings of positive relative resistance by M. Colci et al. [Phys. Rev. B 85, 180512(R) (2012)] as well as previously measured negative relative resistance results, both within sufficiently large parameter regions.