Direct evidence of hidden local spin polarization in a centrosymmetric superconductor LaO0.55 F0.45BiS2

Shi-Long Wu; Kazuki Sumida; Koji Miyamoto; Kazuaki Taguchi; Tomoki Yoshikawa; Akio Kimura; Yoshifumi Ueda; Masashi Arita; Masanori Nagao; Satoshi Watauchi; Isao Tanaka; Taichi Okuda

doi:10.1038/s41467-017-02058-2

Direct evidence of hidden local spin polarization in a centrosymmetric superconductor LaO_0.55 F_0.45BiS₂

Nat Commun. 2017 Dec 4;8(1):1919. doi: 10.1038/s41467-017-02058-2.

Authors

Affiliations

¹ Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
² Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan.
³ Center for Crystal Science and Technology (CCST), University of Yamanashi, 7-32 Miyamae, Kofu, Yamanashi, 400-8511, Japan.
⁴ Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan. okudat@hiroshima-u.ac.jp.

Abstract

Conventional Rashba spin polarization is caused by the combination of strong spin-orbit interaction and spatial inversion asymmetry. However, Rashba-Dresselhaus-type spin-split states are predicted in the centrosymmetric LaOBiS₂ system by recent theory, which stem from the local inversion asymmetry of active BiS₂ layer. By performing high-resolution spin- and angle-resolved photoemission spectroscopy, we have investigated the electronic band structure and spin texture of superconductor LaO_0.55F_0.45BiS₂. Here we present direct spectroscopic evidence for the local spin polarization of both the valence band and the conduction band. In particular, the coexistence of Rashba-like and Dresselhaus-like spin textures has been observed in the conduction band. The finding is of key importance for fabrication of proposed dual-gated spin-field effect transistor. Moreover, the spin-split band leads to a spin-momentum locking Fermi surface from which superconductivity emerges. Our demonstration not only expands the scope of spintronic materials but also enhances the understanding of spin-orbit interaction-related superconductivity.