title: Quasiparticle-mediated spin Hall effect in a superconductor.
abstract: In some materials the competition between superconductivity and magnetism brings about a variety of unique phenomena such as the coexistence of superconductivity and magnetism in heavy-fermion superconductors or spin-triplet supercurrent in ferromagnetic Josephson junctions. Recent observations of spin-charge separation in a lateral spin valve with a superconductor evidence that these remarkable properties are applicable to spintronics, although there are still few works exploring this possibility. Here, we report the experimental observation of the quasiparticle-mediated spin Hall effect in a superconductor, NbN. This compound exhibits the inverse spin Hall (ISH) effect even below the superconducting transition temperature. Surprisingly, the ISH signal increases by more than 2,000 times compared with that in the normal state with a decrease of the injected spin current. The effect disappears when the distance between the voltage probes becomes larger than the charge imbalance length, corroborating that the huge ISH signals measured are mediated by quasiparticles.
authors.affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Wakamura
authors.affiliation: Department of Quantum Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Akaike
authors.affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Omori
authors.affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Niimi
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Quantum Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Fujimaki
authors.affiliation: 1] CREST, Japan Science and Technology, Tokyo 102-0075, Japan [2] Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Maekawa
authors.affiliation: 1] Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan [2] RIKEN-CEMS, 2-1 Hirosawa, Wako 351-0198, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Otani