All-Electric Topological Phase Transitions in Proximity-Coupled Bilayer MnBi2Te4 Heterostructures

Abstract

The intrinsic magnetic topological insulator MnBi2Te4, in the two-dimensional limit, hosts thickness dependent axion and quantum anomalous Hal (QAH) insulating states governed by antiferromagnetic interlayer coupling. However, controlled interconversion between these phases typically requires extreme external magnetic fields exceeding 9 T, limiting practical tunability. Using complementary first-principles calculations and effective Hamiltonian modeling, we demonstrate a field-free, reversible mechanism to engineer topological phase transitions by exploiting magnetic proximity at the interfaces with a ferromagnetic insulator. Gate-tunable magnetic anisotropy within the ferromagnetic insulator dynamically modulates the proximity-induced exchange bias, enabling all-electric switching of interlayer coupling and band topology in ultrathin MnBi2Te4. Crucially, long-range Heisenberg Monte Carlo simulations reveal that the magnetic ordering temperature of the encapculated MnBi2Te4 film is dramatically elevated. By eliminating the high-field requirement and simultaneously improving thermal stability, this gate-tunable paradigm solves a critical bottleneck in topological physics and offers a viable route toward scalable, high-temperature topological electronics.