Pressure-Tunable Phase Transitions in Atomically Thin Chern Insulator MnBi ₂ Te ₄

Topological insulators lacking time-reversal symmetry can exhibit the quantum anomalous Hall effect. Odd-layer thick MnBi₂Te₄ is a promising platform due to its intrinsic magnetic nature; however, quantization is rarely observed in it. Our magnetoresistance measurements in the antiferromagnetic phase indicate, instead of a quantum anomalous Hall insulator, the presence of a trivial insulator state likely due to disorder, while in a high magnetic field, a Chern insulator state appears. From the magnetic field and temperature dependence, we estimate that the interlayer exchange coupling is enhanced by hydrostatic pressure while the intralayer coupling is weakened. The trivial band gap is also reduced, suggesting the role of disorder is weakened upon compression of the layers.