Spin-polarized saddle points in the topological surface states of the elemental Bismuth revealed by a pump-probe spin-resolved ARPES

• DOI: 10.48550/arxiv.2303.17816
• Publication Date: 2023-01-01
• Authors: Fukushima, Yuto; Kawaguchi, Kaishu; Kuroda, Kenta; Ochi, Masayuki; Tanaka, Hiroaki; Harasawa, Ayumi; Iimori, Takushi; Zhao, Zhigang; Tani, Shuntaro; Yaji, Koichiro; Shin, Shik; Komori, Fumio; Kobayashi, Yohei; Kondo, Takeshi
• Keywords: Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences

We use a pump-probe, spin-, and angle-resolved photoemission spectroscopy (ARPES) with a 10.7 eV laser accessible up to the Brillouin zone edge, and reveal for the first time the entire band structure, including the unoccupied side, for the elemental bismuth (Bi) with the spin-polarized surface states. Our data identify Bi as in a strong topological insulator phase ($Z_2$=1) against the prediction of most band calculations. We unveil that the unoccupied topological surface states possess spin-polarized saddle points yielding the van Hove singularity, providing an excellent platform for the future development of opto-spintronics.<br/>6 pages, 4 figures<br/>