Observation of topological Anderson Chern insulator phase in MnBi$_4$Te$_7$ monolayer

TL;DR

This paper reports the first experimental observation of a topological Anderson Chern insulator in a monolayer MnBi$_4$Te$_7$, demonstrating disorder-induced topological phase transition with quantized Hall conductance.

Contribution

It provides experimental evidence of a topological Anderson insulator in a solid state system, confirming theoretical predictions about disorder-induced topological phases.

Findings

Observation of quantized Hall plateau and zero longitudinal resistance.

Disorder-induced transition from trivial to nontrivial topological state.

Evidence of universal conductance fluctuations supporting the phase transition.

Abstract

The correlation of topology and disorder has attracted great intention due to appropriate disorder could induce the phase transition between trivial and nontrivial topological states. While it is widely recognized that strong disorder can produce rich phase diagrams in topological nontrivial states, moderate disorder has been proposed to induce transitions into topologically nontrivial phases counter-intuitively, leading to the concept of topological Anderson insulators. This phenomenon has been theoretically explored and simulated in various systems, yet experimental realization in solid state systems has remained elusive due to challenges in controlling disorder. Here, we report the experimental observation of Chern insulator state signed by the coexistence of quantized Hall plateau and zero longitudinal resistance in monolayer MnBi$_4$Te$_7$ Hall bar device, which originally hosts a trivial insulating state with Chern number $C$ = 0 in clean limit. We demonstrate that the observed trivial to nontrivial transition in this monolayer device can be attributed to disorder, evidenced by universal conductance fluctuations. Our findings substantiate the existence of a long-sought topological Anderson Chern insulator in real materials, a unique variant of the topological Anderson insulator characterized by broken time-reversal-symmetry.