Spin Polarized Triplet Supercurrent in Ferromagnetic-Superconducting Josephson Junctions*

Proximity coupling across superconductor-ferromagnet bilayers can give rise to the triplet component of the superconducting condensate [1]. Superconductivity and ferromagnetism have been reported to coexist in a Ni/Bi bilayer system [2]. We investigated Josephson and quasiparticle tunneling across such ferromagnetic-superconducting layers in Bi/Ni/Insulator/Ni/Bi junctions. The superconductivity in the Ni/Bi bilayer is expected to be topological [3]. Moreover, the observed Josephson current could be spin polarized, as superconducting quasiparticles originating from Ni in the Ni/Bi bilayer have been shown to also exhibit spin polarization [2]. The occurrence of conductance at zero bias in these junctions points to odd-frequency symmetry in the superconducting condensate, supporting the presence of a non-zero component associated with a triplet pair superconductivity insensitive to disorder.
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