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.
@article{arxiv.2511.04879,
title = {In-Plane Field induced Quantized Longitudinal Conductivity in Magnetic Topological Insulators},
author = {Ting-Hsun Yang and Yaochen Li and Peng Zhang and Penghao Zhu and Hung-Yu Yang and Eun Sang Choi and Kaiwei Chen and Wenqiang Cui and Kin Wong and Peng Deng and Gang Qiu and Kang L. Wang},
journal= {arXiv preprint arXiv:2511.04879},
year = {2025}
}