Type-I and Type-II Saddle Points and a Topological Flat Band in a Bi-Pyrochlore Superconductor CsBi2
By combining angle-resolved photoemission spectroscopy and first-principles calculations, this study reveals that the Laves-phase superconductor CsBi2 hosts a dispersionless topological flat band and coupled type-I and type-II saddle points that collectively generate a large electron density of states, offering a novel mechanism for enhancing many-body interactions in three-dimensional systems with strong spin-orbit coupling.
Yusei Morita, Yongkai Li, Yu-Hao Wei, Kosuke Nakayama, Zhiwei Wang, Hua-Yu Li, Takemi Kato, Seigo Souma, Kiyohisa Tanaka, Kenichi Ozawa, Jia-Xin Yin, Takashi Takahashi, Min-Quan Kuang, Yugui Yao, Taka (…)2026-04-10🔬 cond-mat.mes-hall