Masashi Shiraishi

Affiliation

• Department of Electronic Science and Engineering, Kyoto Univ., 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 Dirac­like linear band structure. The

surface state is topologically protected due to existence of the Chern­Simons 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 so­called spin­momentum

locking. Thus, much effort has been paid for its detection. Angle­resolved 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 3­terminal

method allows to detect the spin­momentum 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.

These studies were implemented by collaboration with Prof. Yoichi Ando (Univ. Koern,

Germany), Prof. Akio Kimura (Hiroshima Univ., Japan), Dr. Yuichiro Ando and Dr. Gaku

Eguchi (Kyoto University, Japan).

References

• [1] Yuichiro Ando, Yoichi Ando, Masashi Shiraishi et al., Nano Letters 14, 6226 (2014).

• [2] Gaku Eguchi, Akio Kimura, Masashi Shiraishi et al., Physical Review B90, 201307(R),

2014.