Large Chern Number Quantum Anomalous Hall Effect In Thin-film Topological Crystalline Insulators

TL;DR

This paper predicts that thin-film topological crystalline insulators doped with ferromagnetic materials can host quantum anomalous Hall states with tunable Chern numbers from -4 to 4, offering potential for low-power electronic applications.

Contribution

It introduces a theoretical framework for achieving various Chern numbers in doped TCI thin films, expanding the possibilities beyond previously observed Chern numbers.

Findings

Chern number can be tuned between -4 and 4 in doped TCI thin films.

Multiple factors such as Zeeman field, structural distortion, and film thickness influence the Chern number.

Potential for ultra-low power electronic applications due to tunable topological states.

Abstract

Quantum anomalous Hall (QAH) insulators are two-dimensional (2D) insulating states exhibiting properties similar to those of quantum Hall states but without external magnetic field. They have quantized Hall conductance $\sigma^H=Ce^2/h$, where integer $C$ is called the Chern number, and represents the number of gapless edge modes. Recent experiments demonstrated that chromium doped thin-film (Bi,Sb)$_2$Te$_3$ is a QAH insulator with Chern number $C=\pm1$. Here we theoretically predict that thin-film topological crystalline insulators (TCI) can host various QAH phases, when doped by ferromagnetically ordered dopants. Any Chern number between $\pm4$ can, in principle, be reached as a result of the interplay between (a) the induced Zeeman field, depending on the magnetic doping concentration, (b) the structural distortion, either intrinsic or induced by a piezoelectric material through proximity effect and (c) the thickness of the thin film. The tunable Chern numbers found in TCI possess significant potential for ultra-low power information processing applications.