Orbital Complexity in Intrinsic Magnetic Topological Insulators MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$

TL;DR

This study uses advanced spectroscopy and theoretical calculations to analyze the complex surface electronic structures of magnetic topological insulators MnBi4Te7 and MnBi6Te10, revealing how surface termination affects their topological properties.

Contribution

It provides detailed experimental and theoretical insights into the orbital and spin textures of these materials, clarifying their topological nature and the impact of surface termination on their electronic states.

Findings

Dirac-cone surface state is perturbed by hybridization on Bi2Te3-terminated surfaces.

Topological surface state remains intact on MnBi2Te4-terminated surfaces.

Surface termination influences the potential for quantized anomalous Hall effect.

Abstract

Using angle-resolved photoelectron spectroscopy (ARPES), we investigate the surface electronic structure of the magnetic van der Waals compounds MnBi$_4$Te$_7$ and MnBi$_6$Te$_{10}$, the $n=$~1 and 2 members of a modular (Bi$_2$Te$_3$)$_n$(MnBi$_2$Te$_4$) series, which have attracted recent interest as intrinsic magnetic topological insulators. Combining circular dichroic, spin-resolved and photon-energy-dependent ARPES measurements with calculations based on density functional theory, we unveil complex momentum-dependent orbital and spin textures in the surface electronic structure and disentangle topological from trivial surface bands. We find that the Dirac-cone dispersion of the topologial surface state is strongly perturbed by hybridization with valence-band states for Bi$_2$Te$_3$-terminated surfaces but remains preserved for MnBi$_2$Te$_4$-terminated surfaces. Our results firmly establish the topologically non-trivial nature of these magnetic van der Waals materials and indicate that the possibility of realizing a quantized anomalous Hall conductivity depends on surface termination.