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

TL;DR

This paper demonstrates that the quantum anomalous Hall effect can be tuned in spin-splitting antiferromagnets through crystal order manipulation, expanding control methods beyond magnetic order in topological materials.

Contribution

It introduces a novel approach to control QAH effect via crystal order in antiferromagnets, challenging the conventional reliance on magnetic order.

Findings

Chern number can be modulated by crystal order in antiferromagnets.

Interlayer rotation and translation in 2D MnBi2Te4 induce QAH transition.

Crystal design enables reversible Chern number control in 2D materials.

Abstract

Quantum anomalous Hall (QAH) effect provides dissipationless chiral channels for spin transport, expected as an outstanding candidate in future low-power quantum computation. The spin-splitting band structure is vital for obtaining QAH effect in topological systems, with ferromagnetism indispensable to manipulate the Chern number. Herein, we challenge this wisdom by proposing tunable QAH effect in spin-splitting antiferromagnets with zero magnetization. Since the spin splitting of these unique magnets originates from the alternate crystal environment, the Chern number can be modulated not only by the conventional magnetic order, but also by the crystal order, opening an additional dimension for tuning QAH effect. Our concept is illustrated based on two-dimensional (2D) MnBi2Te4 (MBT) with even septuple layers (SLs), a typical axion insulator 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 the QAH insulator. The flexible stacking of 2D materials enables the reversible Chern number by crystal design. Our work fundamentally reveals the crystal-order-dependent QAH effect in spin-splitting antiferromagnets, which would advance QAH effect-based devices towards high controllability, integration density and operation speed.