Characterization of the Layered Antiferromagnetic Topological Insulator MnBi2Se4 Using Scanning Tunneling Microscopy

Recently, topological insulators have been an area of interest due to the existence of symmetry protected states. Those with broken time reversal symmetry are particularly interesting because they have been predicted to host several intriguing phenomena such as the quantum anomalous hall effect, magneto-electric effects, and topologically protected surface and edge states. MnBi2Se4 (MBS) is a predicted topological insulator formed of van der Waals separated septuple layers (SL) with a layered anti-ferromagnetic structure, which breaks time-reversal symmetry and could therefore potentially realize some of those phenomena. For this study, a Se capped 20SL MBS film was grown on a sapphire substrate using molecular beam epitaxy. After other measurements were taken ex-situ the sample was then de-capped and transferred via vacuum suitcase to a low-temperature (5K) scanning tunneling microscope (STM). In our STM images, we observed a triangular lattice with an average lattice constant of 3.85Å. Additionally, we see a semiconducting nature in scanning tunneling spectroscopy with a band gap of approximately 700meV.