Van Hove Singularity Arising from Mexican-Hat-Shaped Inverted Bands in the Topological Insulator Sn-doped Bi$_{1.1}$Sb$_{0.9}$Te$_{2}$S

Wenchao Jiang; Bowen Li; Xiaomeng Wang; Guanyu Chen; Tong Chen; Ying Xiang; Wei Xie; Yaomin Dai; Xiyu Zhu; Huan Yang; Jian Sun; Hai-Hu Wen

doi:10.1103/PhysRevB.101.121115

paper

Van Hove Singularity Arising from Mexican-Hat-Shaped Inverted Bands in the Topological Insulator Sn-doped Bi $_{1.1}$ Sb $_{0.9}$ Te $_{2}$ S

arXiv:2101.02970 · doi:10.1103/PhysRevB.101.121115

Abstract

The optical properties of Sn-doped Bi $_{1.1}$ Sb $_{0.9}$ Te $_{2}$ S, the most bulk-insulating topological insulator thus far, have been examined at different temperatures over a broad frequency range. No Drude response is detected in the low-frequency range down to 30~cm $^{- 1}$ , corroborating the excellent bulk-insulating property of this material. Intriguingly, we observe a sharp peak at about 2\,200~cm $^{- 1}$ in the optical conductivity at 5~K. Further quantitative analyses of the line shape and temperature dependence of this sharp peak, in combination with first-principles calculations, suggest that it corresponds to a van Hove singularity arising from Mexican-hat-shaped inverted bands. Such a van Hove singularity is a pivotal ingredient of various strongly correlated phases.

6 pages, 4 figures

Van Hove Singularity Arising from Mexican-Hat-Shaped Inverted Bands in the Topological Insulator Sn-doped Bi1.1​Sb0.9​Te2​S

Abstract

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Van Hove Singularity Arising from Mexican-Hat-Shaped Inverted Bands in the Topological Insulator Sn-doped Bi $_{1.1}$ Sb $_{0.9}$ Te $_{2}$ S