Bulk and surface electronic structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Bi</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Te</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>G</mml:mi><mml:mi>W</mml:mi></mml:mrow></mml:math> calculations and photoemission experiments

Abstract

We present a combined theoretical and experimental study of the electronic structure of stoichiometric ${\mathrm{Bi}}_{4}{\mathrm{Te}}_{3}$, a natural superlattice of alternating ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ quintuple layers and Bi bilayers. In contrast to the related semiconducting compounds ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ and ${\mathrm{Bi}}_{1}{\mathrm{Te}}_{1}$, density functional theory predicts ${\mathrm{Bi}}_{4}{\mathrm{Te}}_{3}$ is a semimetal. In this work, we compute the quasiparticle electronic structure of ${\mathrm{Bi}}_{4}{\mathrm{Te}}_{3}$ in the framework of the $GW$ approximation within many-body perturbation theory. The quasiparticle corrections are found to modify the dispersion of the valence and conduction bands in the vicinity of the Fermi energy, leading to the opening of a small indirect band gap. Based on the analysis of the eigenstates, ${\mathrm{Bi}}_{4}{\mathrm{Te}}_{3}$ is classified as a dual topological insulator with bulk topological invariants ${\mathbb{Z}}_{2} (1;111)$ and magnetic mirror Chern number ${n}_{M}=1$. The bulk $GW$ results are used to build a Wannier-function-based tight-binding Hamiltonian that is further applied to study the electronic properties of the (111) surface. The comparison with our angle-resolved photoemission measurements shows excellent agreement between the computed and measured surface states and indicates the dual topological nature of ${\mathrm{Bi}}_{4}{\mathrm{Te}}_{3}$.

Topics & Concepts