Visualization of spin-polarized surface resonances in Pb-based ternary topological insulators

Koichiro Yaji; Yuya Hattori; Shunsuke Yoshizawa; Shunsuke Tsuda; Fumio Komori; Youhei Yamaji; Yuto Fukushima; Kaishu Kawaguchi; Takeshi Kondo; Yuki Tokumoto; Keiichi Edagawa; Taichi Terashima

doi:10.1038/s41598-024-76493-9

Visualization of spin-polarized surface resonances in Pb-based ternary topological insulators

Sci Rep. 2024 Oct 28;14(1):25868. doi: 10.1038/s41598-024-76493-9.

Authors

Koichiro Yaji^{1

2}, Yuya Hattori³, Shunsuke Yoshizawa³, Shunsuke Tsuda⁴, Fumio Komori^{4

5}, Youhei Yamaji⁶, Yuto Fukushima⁷, Kaishu Kawaguchi⁷, Takeshi Kondo^{7

8}, Yuki Tokumoto⁵, Keiichi Edagawa⁵, Taichi Terashima⁹

Affiliations

¹ Center for Basic Research on Materials, National Institute for Materials Science (NIMS), 3-13, Sakura, Tsukuba, 305-0003, Ibaraki, Japan. yaji.koichiro@nims.go.jp.
² Unprecedented-Scale Data Analytics Center, Tohoku University, 468-1 Aoba, Aramaki-Aza, Aoba-Ku, Sendai, 980-8578, Japan. yaji.koichiro@nims.go.jp.
³ Center for Basic Research on Materials, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, 305-0047, Ibaraki, Japan.
⁴ Center for Basic Research on Materials, National Institute for Materials Science (NIMS), 3-13, Sakura, Tsukuba, 305-0003, Ibaraki, Japan.
⁵ Institute of Industrial Science, The University of Tokyo, Komaba, Tokyo, 153-8505, Japan.
⁶ Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0003, Ibaraki, Japan.
⁷ Institute for Solid State Physics, The University of Tokyo, Kashiwa, 277-8581, Chiba, Japan.
⁸ Trans-Scale Quantum Science Institute, The University of Tokyo, Bunkyo-Ku, Tokyo, 113-0033, Japan.
⁹ Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 3-13, Sakura, Tsukuba, 305-0003, Ibaraki, Japan.

Abstract

The formation of the topological surface state originates from bulk band inversion at the top of the valence band and the bottom of the conduction band. The transition between normal and topological insulators is known as a topological phase transition. Here we show spin-polarized electronic states of Pb-based ternary topological insulators Pb(Bi_1-xSb_x)₂Te₄ (x = 0.55, 0.70, 0.79) investigated by spin- and angle-resolved photoemission spectroscopy and first-principles calculations. We visualize a pair of spin-polarized surface resonances dispersing along the upper edge of projected bulk bands in occupied states. Interestingly, a branch of the spin-polarized surface resonances continuously connects to the topological surface state. The coexistence of the topological surface state and the spin-polarized surface resonances can be explained by considering the topological phase transition.

Keywords: Spin-resolved photoemission spectroscopy; Surface resonance; Topological insulator.