Gate-tunable giant anomalous Hall effect in magnetic topological insulator bilayer

Abstract

In the two-dimensional limit, the intrinsic magnetic topological insulator MnBi2Te4 provides a compelling platform for exploring thickness-dependent quantum states and their evolution under external perturbations. Using first-principles calculations and classical Heisenberg Monte Carlo simulations, we demonstrate that electrostatic gating and surface chemical functionalization can drive a systematic crossover from the topological to the conventional anomalous Hall regime. This transition is governed by the simultaneous shift of the Fermi level away from the topological gap and a reversal of interlayer coupling from antiferromagnetic to ferromagnetic order. Results reveal that hole doping drives the Fermi level into the valence bands, inducing an exceptionally high anomalous Hall conductivity of 1127 S/cm arising from Berry curvature hot spots. In contrast, surface chemical doping drives a topological state where intrinsic $\sigma_{xy}$ is reduced from $e^2/h$ to $\sim 0.86\ e^2/h$ by the spectral coexistance of chiral edge mode with metallic bulk states of the two-dimensional film. Furthermore, we show that both tuning routes significantly enhance in-plane exchange interactions, leading to a substantial increase in the magnetic ordering temperature relative to the pristine bilayer. These results establish a versatile framework for the simultaneous engineering of topological, magnetic, and transport properties in ultrathin MnBi2Te4, offering direct implications for the development of reconfigurable quantum devices.