The superconducting absolute spin valve

A ferromagnetic insulator, such as EuS, in contact with a superconductor drives an exchange field resulting in a splitting of the Bardeen-Cooper-Schrieffer density of states by a magnitude proportional to its magnetization [1]. It was suggested that the combination of two such spin-split superconductors could implement an ideal spin valve [2]: a hybrid ferromagnetic-superconducting tunnel junction where the transport of one of the spin species is open while it is completely blocked for the other. Here we report on a switchable superconducting spin-valve based on two EuS/Al bilayers coupled through a tunnel barrier. Our devices exhibit a relative differential resistance variation -between the parallel and antiparallel configuration of the EuS layers- up to almost 1000%. Our devices implement an efficient spin polarized current source and can be exploited as switching logical elements in a memory cell to be used in cryogenics superconductor-based computers.

[1] E. Strambini et al, Phys. Rev. Materials 1, 054402 (2017)
[2] D. Huertas-Hernando, et al., Physical Review Letters 88(4), 47003 (2002)