Anomalous Interference of Floquet-Bloch States in the Magnetic Topological Insulator MnBi₂Te₄

The coherent optical manipulation of solids via Floquet engineering has emerged as a promising way to understand non-equilibrium physics and generate novel quantum phases of matter. So far, Floquet engineering of materials has been limited to Dirac materials without strong correlations. Here we use time- and angle-resolved photoemission spectroscopy (tr-ARPES) with mid-IR pump pulses to observe Floquet-Bloch states in the intrinsic antiferromagnetic topological insulator MnBi₂Te₄. This system is an ideal candidate for studying Floquet phenomena in the presence of both magnetic correlations and topology. We observe an anomalous interference between certain Floquet-Bloch states which is distinct from the well characterized Floquet-Bloch response of the 3D topological insulator Bi₂Se₃. We will discuss this observation in relation to the intrinsic antiferromagnetic ordering and topological character of MnBi₂Te₄.