Kuei Sun, Nayana Shah, Smitha Vishveshwara
We study electronic transport in junctions consisting of a superconductor electrode and two ferromagnet (F) leads in which crossed Andreev reflections (CAR) and elastic co-tunnelings are accommodated. We model the system using an extended Blonder-Tinkham-Klapwijk (BTK) 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 resistance between the parallel and antiparallel alignments of the magnetization of the F leads. Our model accounts for the surprising experimental findings of positive relative resistance by 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.
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http://arxiv.org/abs/1209.4478
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