Kavli Affiliate: Mamoru Matsuo
| First 5 Authors: Dapeng Yao, Mamoru Matsuo, Takehito Yokoyama, ,
| Summary:
The recent experiment [R. Nakajima, et al., Nature 613, 479 (2023)] has
reported a pair of oppositely polarized spins under an alternating electric
current in a superconductor with a chiral structure. However, these behaviors
cannot be explained by the conventional Edelstein effect and require a new
mechanism. In this Letter, we propose a mechanism of spin current generation
under an external electric field due to chiral phonons in a chiral-structure
superconductor based on the Bogoliubov de Gennes and the Boltzmann equations.
In our mechanism, chiral phonons are induced by electric field due to inversion
symmetry breaking and electron-phonon interaction. They work as an effective
Zeeman field and hence spin-polarize Bogoliubov quasiparticles in the
superconductor. As a result, the spin current carried by quasiparticles flows
along the screw axis and shows a quadratic dependence on the electric field at
the low-field range, leading to a nonreciprocal spin transport. The spin
current also shows a nonmonotonic temperature dependence and has a maximum at
around the superconducting transition temperature.
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