Universal correspondence between edge spin accumulation and equilibrium spin currents in nanowires with spin-orbit coupling

Physical Review B 100, 214422 (2019)

Universal correspondence between edge spin accumulation and equilibrium spin currents in nanowires with spin-orbit coupling

I. V. Tokatly, B. Bujnowski, F. S. Bergeret

Although equilibrium spin currents (ESCs) may exist in materials with spin-orbit coupling, they are not transport currents and cannot lead to spin accumulation in the presence of time-reversal symmetry. It is for this reason that the detection of ESCs has remained elusive. Here we show that in a nanowire with spin-orbit coupling, breaking the time-reversal symmetry by a Zeeman field leads to a bulk equilibrium spin current which manifests itself in a sizable edge spin polarization, transverse to the Zeeman field. The net accumulated spin does not depend on specific properties of the wire ends, being fully determined by the bulk spin current. This bulk-boundary correspondence is a universal property that occurs in both the normal and superconducting states independently of the degree of disorder. The transverse edge spin polarization is strongly enhanced in the superconducting state when the Zeeman energy is of the order of the induced superconducting gap. This leads to a hitherto unknown transverse magnetic susceptibility that can be much larger than the longitudinal, and it drastically changes the paramagnetic response of the nanowire.

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http://dx.doi.org/10.1103/PhysRevB.100.214422
arxiv
http://arxiv.org/abs/arXiv:1901.07890

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