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arXiv · 1710.02161

Creation of spin-triplet Cooper pairs in the absence of magnetic ordering

Daniel Breunig·Pablo Burset·Björn Trauzettel
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Abstract

In superconducting spintronics, it is essential to generate spin-triplet Cooper pairs on demand. Up to now, proposals to do so concentrate on hybrid structures in which a superconductor (SC) is combined with a magnetically ordered material (or an external magnetic field). We, instead, identify a novel way to create and isolate spin-triplet Cooper pairs in the absence of any magnetic ordering. This achievement is only possible because we drive a system with strong spin-orbit interaction--the Dirac surface states of a strong topological insulator (TI)--out of equilibrium. In particular, we consider a bipolar TI-SC-TI junction, where the electrochemical potentials in the outer leads differ in their overall sign. As a result, we find that nonlocal singlet pairing across the junction is completely suppressed for any excitation energy. Hence, this junction acts as a perfect spin triplet filter across the SC generating equal-spin Cooper pairs via crossed Andreev reflection.

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Daniel Breunig, Pablo Burset, Björn Trauzettel. 2017-10-05. Creation of spin-triplet Cooper pairs in the absence of magnetic ordering. https://doi.org/10.1103/physrevlett.120.037701

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