Giant spin splitting and 0−π Josephson transitions from the Edelstein effect in quantum spin Hall insulators

G. Tkachov

doi:10.1103/PhysRevB.95.245407

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Giant spin splitting and 0−π Josephson transitions from the Edelstein effect in quantum spin Hall insulators

G. Tkachov

DOI 10.1103/PhysRevB.95.245407 · Physical Review B

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Abstract

Hybrid structures of quantum spin Hall insulators (QSHIs) and superconductors (Ss) present a unique opportunity to access dissipationless topological states of matter, which, however, is frequently hindered by the lack of control over the spin polarization in QSHIs. We propose a very efficient spin-polarization mechanism based on the magnetoelectric (Edelstein) effect in superconducting QSHI structures. It acts akin to the Zeeman splitting in an external magnetic field, but with an effective g factor of order of 1000, resulting in an unprecedented spin splitting effect. It allows a magnetic control of the QSHI/S hybrids without destroying superconductivity. As an example, we demonstrate a recurrent crossover from Φ0- to (Φ0/2)-periodic oscillations of the Josephson current in an rf superconducting quantum interference device (Φ0=h/2e is the magnetic flux quantum). The predicted period halving is a striking manifestation of 0−π Josephson transitions with a superharmonic π-periodic current-phase relationship at the transition. Such controllable 0−π transitions may offer new perspectives for dissipationless spintronics and engineering flux qubits.