Axion insulator states in a topological insulator proximitized to magnetic insulators: A tight-binding characterization

Abstract

The recent discovery of axion states in materials such as antiferromagnetic topological insulators has boosted investigations of the magnetoelectric response in topological insulators and their promise towards realizing dissipationless topological electronics. In this paper, we develop a tight-binding methodology to explore the emergence of axion states in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ in proximity to magnetic insulators on the top and bottom surfaces. The topological protection of the surface states is lifted by a time-reversal-breaking perturbation due to the proximity of a magnetic insulator, and a gap is opened on the surfaces, giving rise to half-quantized Hall conductance and a zero Hall plateau---evidencing an axion insulator state. We developed a real-space tight-binding Hamiltonian for ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ using first-principles data. Transport properties of the system were obtained within the Landauer-B\"uttiker formalism, and we discuss the creation of axion states through Hall conductance and a zero Hall plateau at the surfaces, as a function of proximitized magnetization and corresponding potentials at the surfaces, as well as the thickness of the topological insulator.