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Register a new userGiant spin splitting and $0 - pi$ Josephson transitions from the Edelstein effect in quantum spin-Hall insulators
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Authors
G. Tkachov
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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 $Phi_0$ - to $Phi_0/2$ - periodic oscillations of the Josephson current in an rf superconducting quantum interference device ($Phi_0=h/2e$ is the magnetic flux quantum). The predicted period halving is a striking manifestation of $0-pi$ Josephson transitions with a superharmonic $pi$-periodic current-phase relationship at the transition. Such controllable $0-pi$ transitions may offer new perspectives for dissipationless spintronics and engineering flux qubits.
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In an easy-plane antiferromagnet with the Dzyaloshinskii-Moriya interaction (DMI), magnons are subject to an effective spin-momentum locking. An in-plane temperature gradient can generate interfacial accumulation of magnons with a specified polarization, realizing the magnon thermal Edelstein effect. We theoretically investigate the injection and detection of this thermally-driven spin polarization in an adjacent heavy metal with strong spin Hall effect. We find that the inverse spin Hall voltage depends monotonically on both temperature and the DMI but non-monotonically on the hard-axis anisotropy. Counterintuitively, the magnon thermal Edelstein effect is an even function of a magnetic field applied along the Neel vector.
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