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

arXiv · 2101.02970

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

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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.

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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. 2021-01-08. 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. https://doi.org/10.1103/physrevb.101.121115

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