Masashi Shiraishi

Affiliation

• Department of Electronic Science and Engineering, Kyoto University, Japan

Title

Electrical detection of surface spin polarization due to spin­-momentum locking in BiSbTeSe

Abstract

Topological insulator (TI) is a new class of a condensed matter, where a bulk state is insulating and a surface (or an edge) state has the Dirac-­like linear band structure. The surface state is topologically protected due to existence of the Chern­-Simons term and the gauge invariance conservation. In consequence, the state is in principle 100% spin polarized, i.e., a persistent pure spin current exists due to a so­-called spin­-momentum locking. Thus, much effort has been paid for its detection. Angle ­resolved photoemission spectroscopy has been the most potential method for the detection, but recently, an electrical method enables to detect the surface spin polarization. Here we introduce the detection of the surface spin polarization of a TI, BiSbTeSe(BSTS) [1], which is the first bulk insulating TI. In this study, a local 3-terminal method allows to detect the spin­-momentum locking in BSTS, and the spin accumulation beneath a ferromagnetic electrode was successfully detected up to 125 K. The detail of the experiments and discussion will be discussed in the presentation. Furthermore, we briefly show transport properties of the first hole carrier TI, TlBiSe [2], if time permits.

Collaborators

• Yoichi Ando, University of Koern, Germany
• Akio Kimura, Hiroshima University, Japan
• Yuichiro Ando, Kyoto University, Japan
• Gaku Eguchi, Kyoto University, Japan

References

• [1] Y. Ando, T. Hamasaki, T. Kurokawa, K. Ichiba, F. Yang, M. Novak, S. Sasaki, K. Segawa, Y. Ando, and M. Shiraishi, Electrical detection of the spin polarization due to charge flow in the surface state of the topological insulator Bi_1.5Sb_0.5Te_1.7Se_1.3, Nano Lett. 14, 6226 (2014).

• [2] G. Eguchi, K. Kuroda, K. Shirai, A. Kimura, and M. Shiraishi, Surface Shubnikov–de Haas oscillations and nonzero Berry phases of the topological hole conduction in Tl_1−xBi_1+xSe₂, Phys. Rev. B 90, 201307(R) (2014).