Spin-orbit torque switching of N\'eel order in band-inverted antiferromagnetic bilayer MnBi$_2$Te$_4$

Abstract

Magnetic topological insulators host exotic phenomena such as the quantum anomalous Hall effect and quantized magnetoelectric responses, but dynamic electrical control of their topological phases remains elusive. Here we demonstrate from first principles that spin-orbit torque enables direct electrical switching of the N\'eel configuration in intrinsic antiferromagnetic bilayer MnBi$_2$Te$_4$, thereby reconfiguring its boundary spectrum. A symmetry-allowed interband (time-reversal even) torque persists inside the bulk gap, and deterministically reverses the N\'eel order and layer-resolved Chern marker without free carriers. Upon doping, both interband and intraband torques are amplified, lowering the critical electric field for switching by two orders of magnitude. Together, these results establish two complementary regimes of control: dissipationless in-gap torques without Joule heating and enhanced current-induced torques, providing a robust route to manipulate a layer-resolved Chern marker and helical-like gapped edge modes in antiferromagnetic MnBi$_2$Te$_4$.