Magnetized Topological Insulator Multilayers

TL;DR

This paper models the magnetic and topological properties of magnetized topological insulator multilayers, explaining how stacking and thickness influence phenomena like the quantum anomalous Hall effect, supported by DFT comparisons.

Contribution

It introduces a simplified Dirac-cone model for magnetized topological insulator multilayers, linking structural configurations to topological phenomena and validating with ab initio calculations.

Findings

Model explains dependence of quantum anomalous Hall effect on film thickness and stacking.

Parameters estimated through comparison with density-functional-theory calculations.

Provides insights into designing Weyl superlattices with desired topological properties.

Abstract

We discuss the magnetic and topological properties of bulk crystals and quasi-two-dimensional thin films formed by stacking intrinsic magnetized topological insulator ( for example Mn(Sb$_{x}$Bi$_{1-x}$)$_2$X$_4$ with X = Se,Te, including MnBi$_2$Te$_4$) septuple layers and topological insulator quintuple layers in arbitrary order. Our analysis makes use of a simplified model that retains only Dirac-cone degrees of freedom on both surfaces of each septuple or quintuple layer. We demonstrate the model's applicability and estimate its parameters by comparing with {\it ab initio } density-functional-theory(DFT) calculations. We then employ the coupled Dirac cone model to provide an explanation for the dependence of thin-film properties, particularly the presence or absence of the quantum anomalous Hall effect, on film thickness, magnetic configuration, and stacking arrangement, and to comment on the design of Weyl superlattices.