Layer-dependent antiferromagnetic Chern and axion insulating states in UOTe

TL;DR

This paper predicts layer-dependent topological phases in the antiferromagnetic UOTe, revealing potential for high-temperature magnetic topological insulators with tunable quantum anomalous Hall and axion insulator states.

Contribution

It introduces a systematic layer-dependent analysis of UOTe, predicting novel topological phases and phase transitions driven by strain or electric field in an antiferromagnetic van der Waals material.

Findings

Two-layer UOTe is an AFM Chern insulator with quantized Hall conductivity.

Three-layer UOTe hosts an axion insulator-like state with quantized spin Hall conductivity.

Layer number determines topological phase: odd layers are axion-like, even layers are Chern insulators.

Abstract

Magnetic topological insulators have received significant interest due to their dissipationless edge states, which promise advances in energy-efficient electronic transport. However, the magnetic topological insulator state has typically been found in ferromagnets (FMs) that suffer from low magnetic ordering temperatures and stray fields. Identifying an antiferromagnetic topological insulator that exhibits the quantum anomalous Hall effect (QAHE) with a relatively high N\'eel temperature has been a longstanding challenge. Here, we focus on the recently discovered van der Waals (vdW) antiferromagnet (AFM) UOTe, which not only features a high N\'eel temperature (\(\sim\)150K) but also exhibits intriguing Kondo interaction and topological characteristics. Our systematic analysis of the layer-dependent topological phases based on \textit{ab} initio computations predicts the two-layer UOTe film to be an ideal 2D AFM Chern insulator in which the Hall conductivity is quantized with a fully compensated spin magnetization. By applying an in-plane strain or electric field, we show how the itinerancy of U-5f electrons can be manipulated to trigger a transition between the nontrivial ($C = 1$) and trivial ($C = 0$) phases. Interestingly, the 3-layer UOTe film is found to have zero charge conductance but it hosts a quantized spin Hall conductivity (SHC) with finite magneto-electric coupling, suggesting the presence of an axion insulator-like state. The unique magnetic structure of UOTe supports a layer-tunable topology in which films with an odd number of layers are axion-like insulators, while films with an even number of layers are Chern insulators, and the bulk material is a Dirac semimetal. Our study offers a new intrinsic AFM materials platform for realizing correlated topological phases for next-generation spintronics applications and fundamental science studies.