Magnetization-free quantum anomalous Hall effect in altermagnetic weak topological insulators

Abstract

The quantum anomalous Hall (QAH) effect is usually realized through ferromagnetism or magnetic dop ing, which limits material choices and often results in low mobility, disorder sensitivity, and low operating temperatures. Here, we propose a mechanism to achieve the QAH phase without net magnetization, using altermagnetic exchange on a weak topological insulator (WTI). The altermagnetic order selectively gaps the Dirac cone at the Z point, while hybridization between the top and bottom surfaces of the WTI thin film opens a trivial gap at the point, generating a Chern number C = 1 phase with a single chiral edge channel. We verify the topological transition through both a minimal thin-film model and a slab geometry, and compute the associated Hall response. As altermagnets and layered WTIs already exist experimentally, this mechanism offers a promising and experimentally accessible route to realizing QAH phases without magnetic doping or global magnetization. The results indicate that altermagnetic surface engineering may provide a clean and controllable pathway for realizing dissipationless edge transport in layered quantum materials.

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