Topological Crystalline Insulator and Quantum Anomalous Hall States in IV-VI based Monolayers and their Quantum Wells

TL;DR

This paper predicts that SnTe and PbTe monolayers, even when placed on substrates that break mirror symmetry, can exhibit quantum anomalous Hall effects with large gaps, and these properties are retained in quantum well structures.

Contribution

It introduces a new family of 2D TCIs, demonstrating their potential to host quantum anomalous Hall states even without mirror symmetry.

Findings

Quantum anomalous Hall effect with C=2 predicted in SnTe and PbTe monolayers.

Large-gap topological properties preserved in quantum well structures.

Topological phases are robust despite mirror symmetry breaking.

Abstract

Different from the two-dimensional (2D) topological insulator, the 2D topological crystalline insulator (TCI) phase disappears when the mirror symmetry is broken, e.g., upon placing on a substrate. Here, based on a new family of 2D TCIs - SnTe and PbTe monolayers - we theoretically predict the realization of the quantum anomalous Hall effect with Chern number C = 2 even when the mirror symmetry is broken. Remarkably, we also demonstrate that the considered materials retain their large-gap topological properties in quantum well structures obtained by sandwiching the monolayers between NaCl layers. Our results demonstrate that the TCIs can serve as a seed for observing robust topologically non-trivial phases.