Origins of electronic bands in the antiferromagnetic topological insulator <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>MnBi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>
Chenhui Yan, Sebastian Fernandez-Mulligan, Ruobing Mei, Seng Huat Lee, Nikola Protic, Rikuto Fukumori, Binghai Yan, Chao‐Xing Liu, Zhiqiang Mao, Shuolong Yang
Abstract
Despite the rapid progress in understanding the first intrinsic magnetic topological insulator ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$, its electronic structure remains a topic under debates. Here we perform a thorough spectroscopic investigation into the electronic structure of ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ via laser-based angle-resolved photoemission spectroscopy. Through quantitative analysis, we estimate an upper bound of 3 meV for the gap size of the topological surface state. Furthermore, our circular dichroism measurements reveal band chiralities for both the topological surface state and quasi-2D bands, which can be well reproduced in a band hybridization model. A numerical simulation of energy-momentum dispersions based on a four-band model with an additional step potential near the surface provides a promising explanation for the origin of the quasi-2D bands. Our study represents a solid step forward in reconciling the existing controversies in the electronic structure of ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$, and provides an important framework to understand the electronic structures of other relevant topological materials ${\mathrm{MnBi}}_{2\mathrm{n}}{\mathrm{Te}}_{3\mathrm{n}+1}$.