Enhancement of anomalous Hall effect in epitaxial thin films of intrinsic magnetic topological insulator MnBi₂Te₄ with Fermi-level tuning

The recently discovered intrinsic magnetic topological insulator MnBi₂Te₄ has attracted keen interest for exotic quantum states such as a quantum anomalous Hall insulator and an axion insulator. Such quantum states of MnBi₂Te₄ have been intensively studied mainly in atomically thin exfoliated samples, yet thin film samples with critically tuned Fermi level would be indispensable for further pursuit of topological functionality in MnBi₂Te₄ and related heterointerfaces. Here, we report on fabrication of an Sb-doped MnBi₂Te₄ thin film by molecular beam epitaxy and their transport properties. The Sb-substitution induces the change in the carrier type and the subsequent increase in resistivity, demonstrating the tuning of the Fermi level (E_F) across the bulk bandgap and the phase change to the topologically nontrivial phase. The E_F is further finely controlled in a field-effect transistor device. We observe the enhancement of the anomalous Hall conductivity at the charge neutral point, confirming the opening of the magnetic exchange gap in surface Dirac states. The precise control of the band structure and the Fermi level in the thin-film form will lead to exploring exotic phenomena based on intrinsic magnetic topological insulators.