Spin-Supercurrent and Phase-Tunable Triplet Cooper Pairs via Magnetic Insulators

Ingvild Gomperud, Jacob Linder

Published 2015-03-27Version 1

We demonstrate theoretically that a dissipationless spin-current can flow a long distance through a diffusive normal metal by using superconductors interfaced with magnetic insulators. The magnitude of this spin-supercurrent is controlled via the magnetization orientation of the magnetic insulators. The spin-supercurrent obtained in this way is conserved in the normal metal just like the charge-current and interestingly has a term which is independent of the superconducting phase difference. The quantum state of the system can be switched between 0 and $\pi$ by reversing the insulators from a parallel to antiparallel configuration with an external field. We show that the spin-current is carried through the normal metal by superconducting triplet (odd-frequency) correlations and that the superconducting phase difference can be used to enhance these, leaving clear spectroscopic fingerprints in the density of states.