Superconducting triplet pairings and anisotropic magnetoresistance effects in ferromagnet/superconductor/ferromagnet double-barrier junctions

Abstract

Ferromagnetic spin valves offer the key building blocks to integrate giant- and tunneling-magnetoresistance effects into spintronics devices. Starting from a generalized Blonder-Tinkham-Klapwijk approach, we theoretically investigate the impact of interfacial Rashba and Dresselhaus spin-orbit couplings on the tunneling conductance, and thereby the magnetoresistance characteristics, of ferromagnet/superconductor/ferromagnet spin-valve junctions embedding thin superconducting spacers between the either parallel or antiparallel magnetized ferromagnets. We focus on the unique interplay between usual electron tunnelings-that fully determine the magnetoresistance in the normal-conducting state-and the peculiar Andreev reflections in the superconducting state. In the presence of interfacial spin-orbit couplings, special attention needs to be paid to the spin-flip ("unconventional") Andreev-reflection process that is expected to induce superconducting triplet correlations in proximitized regions. As a transport signature of these triplet pairings, we detect conductance double peaks around the singlet-gap energy, reflecting the competition between the singlet and an additionally emerging triplet gap; the latter is an effective superconducting gap that can be ascribed to the formation of triplet Cooper pairs through interfacial spin-flip scatterings (i.e., to the generation of an effective triplet-pairing term in the order parameter). We thoroughly analyze the Andreev reflections' role in connection with superconducting magnetoresistance phenomena, and eventually unravel huge conductance and magnetoresistance magnetoanisotropies-easily exceeding their normal-state counterparts by several orders of magnitude-as another experimentally accessible fingerprint of unconventional Andreev reflections.

13 pages, 9 figures

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Cited by in corpus (5)

• Microscopic study of the Josephson supercurrent diode effect in Josephson junctions based on two-dimensional electron gas
• Quasiclassical boundary conditions for spin-orbit coupled interfaces with spin-charge conversion
• Unconventional Josephson supercurrent diode effect induced by chiral spin-orbit coupling
• Signatures of superconducting triplet pairing in Ni--Ga-bilayer junctions
• Transport Signatures of Radial Rashba Spin-Orbit Coupling at Ferromagnet/Superconductor Interfaces