In-Plane Field induced Quantized Longitudinal Conductivity in Magnetic Topological Insulators

TL;DR

This paper reports the discovery of an in-plane quantized state in magnetic topological insulators, revealing a new quantum critical point with quantized longitudinal conductivity linked to impurity disorder and gap-closing behavior.

Contribution

It introduces the in-plane quantization (IPQ) state in trilayer magnetic topological insulators and connects it to quantum criticality and impurity effects, providing a new experimental platform.

Findings

Observation of quantized longitudinal conductivity of e2/h under in-plane magnetic fields

Identification of a quantum critical point separating quantum anomalous Hall phases

Role of impurity disorder and electron-hole puddles in stabilizing quantized transport

Abstract

We report the discovery of an in plane quantization (IPQ) state in trilayer magnetic topological insulators, characterized by a quantized longitudinal conductivity of e2/h under strong in-plane magnetic fields. This state emerges at a quantum critical point separating quantum anomalous Hall phases tuned by field angle and orientation, directly linking gap-closing behavior to quantized criticality. Temperature and gate dependent transport measurements, supported by a self consistent approximation model, reveal that electron hole puddles dominate charge transport in this regime, highlighting the essential role of impurity disorder in stabilizing quantized critical transport. These findings establish a tunable experimental framework that connects gap-closing physics with universal conductivity, offering both microscopic insight into critical transport in magnetic topological insulators and a robust platform for probing quantum criticality in topological systems.