Quantized Topological States and Parity Anomaly in Intrinsic Quantum Anomalous Hall Insulator MnBi2Te4

TL;DR

This paper reports the observation of quantized topological states and parity anomaly in high-quality five-layer MnBi2Te4, demonstrating its potential for exploring topological phenomena and quantum devices under high magnetic fields.

Contribution

It provides the first synthesis of high-purity MnBi2Te4 crystals and reveals the role of parity anomaly in governing topological states in this material.

Findings

Observation of quantized topological states in 5-SL MnBi2Te4

Identification of a parity anomaly related to Landau levels

Gate-tunable helical edge transport observed

Abstract

When thinned down to just a few atomic layers, the layered magnetic topological insulator MnBi2Te4 offers an exceptional platform for exploring a wide range of topological phenomena. In this work, we overcome longstanding challenges in synthesizing high-purity MnBi2Te4 crystals and report the observation of a myriad of quantized topological states in high-quality five-septuple-layer (5-SL) samples under magnetic fields up to 45 Tesla. We show that the nontrivial topology of 5-SL MnBi2Te4, in the presence of Landau quantization, is governed by a generalized topological index rooted in the parity anomaly of Dirac fermions in (2+1) dimensions. The anomaly manifests as an anomalous Landau level, giving rise to gate-tunable helical edge transport. Our results establish high-quality MnBi2Te4 as a robust platform for exploring emergent topological states and for advancing novel quantum device applications.