Intrinsic magnetic topological insulator family, [MnTe][Bi₂Te₃]_n, beyond the bulk limit, via atomic-layer-by-layer epitaxy

The intrinsic magnetic topological insulator (IMTI) family [MnTe][Bi₂Te₃]_n exhibits varying magneto-topological properties depending on the choice of n. However, conventional bulk crystal growth methods allow only small values of n, with limited magneto-topological properties. To overcome this, we have utilized the atomic layer-by-layer molecular beam epitaxy (MBE) technique, which enables the formation of arbitrary sequences of MnTe and Bi2Te3 by depositing these two components individually, one at a time. With this technique, we have grown IMTIs with n as large as 16, well beyond the reported values via bulk or thin film synthesis. This enables us to observe a transition in magnetic properties from antiferromagnetic to ferromagnetic, and eventually paramagnetic behavior with increase in n. The novel findings presented in this work pave the way for accelerated progress in the exploration of new IMTI phases, unlocking unexplored magneto-topological properties and applications.