Bi$_{\mathrm{1}}$Te$_{\mathrm{1}}$: A New Dual Topological Insulator
ORAL
Abstract
We present, a combined theoretical and experimental study on the prediction and verification of the dual topological insulating character of the stoichiometric natural superlattice phase Bi$_{\mathrm{1}}$Te$_{\mathrm{1}}$ $=$ [Bi$_{\mathrm{2}}$]$_{\mathrm{1}}$[Bi$_{\mathrm{2}}$Te$_{\mathrm{3}}$]$_{\mathrm{2\thinspace }}$[1]. We identify Bi$_{\mathrm{1}}$Te$_{\mathrm{1}}$ by density functional theory to exhibit a non-trivial time-reversal symmetry-driven character of Z$_{\mathrm{2}} \quad =$ (0; 001) and additionally a mirror-symmetry induced mirror Chern number of v$_{\mathrm{M}} \quad =$ -2, which indicates that Bi$_{\mathrm{1}}$Te$_{\mathrm{1}}$ is both a weak topological insulator (WTI) and a topological crystalline insulator (TCI). The coexistence of the two phenomena preordain distinct crystal planes to host topological surface states that are protected by the respective symmetries. We confirm the stacking sequence of our MBE-grown Bi$_{\mathrm{1}}$Te$_{\mathrm{1}}$ thin films by X-ray diffraction and transmission electron microscopy (STEM), and find clear indications of the TCI and WTI character in the surface spin electronic structure by spin- and angle-resolved photoemission spectroscopy. [1] M. Eschbach et al., arXiv:1604.08886 (2016).
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