Tunable Quantum Anomalous Hall Effect via Crystal Order in Spin-Splitting Antiferromagnets

The quantum anomalous Hall (QAH) effect provides dissipationless channels for spin transport, which is highly expected for low-power quantum computation. Spin-splitting bands are vital for the QAH effect in topological systems, with ferromagnetism indispensable to manipulate the Chern number. Crystal-order-dependent QAH effects in spin-splitting antiferromagnets are proposed here. Since the spin splitting of these antiferromagnets originates from the alternate crystal environment, the Chern number can be modulated by the crystal order, opening an additional dimension for tuning the QAH effect. Our concept is illustrated by two-dimensional (2D) MnBi₂Te₄ (MBT) with even septuple layers, typical axion insulators with fully magnetic compensation. By interlayer rotation and translation operations, sublattices of MBT with opposite magnetizations are no longer connected by inversion or mirror symmetries, leading to the transition to QAH insulators. Flexible stacking of 2D materials enables a reversible Chern number by crystal design. Our findings would advance QAH effect-based devices toward high controllability, integration density, and operation speed.