Tunable Floquet-Bloch manipulation of surface states in the antiferromagnetic topological insulator MnBi₂Te₄

The Floquet-Bloch manipulation of materials using the time-periodic potential of a laser pulse is a promising route to generate and coherently control new phases of matter. So far, experimental realization has been limited to the manipulation of time-reversal symmetric and non-interacting systems such as graphene and the surface states of a 3D topological insulator. In this work, we realize Floquet-Bloch manipulation of a time-reversal broken system: the putative antiferromagnetic topological insulator MnBi₂Te₄. Using time- and angle-resolved photoemission spectroscopy (tr-ARPES) with a mid-infrared pump, we generate Floquet-Bloch sidebands and demonstrate a gap opening at the Dirac point with circularly polarized light. Combined with Floquet theory calculations, our results uncover a rich, tunable Floquet phase diagram that uniquely arises in MnBi₂Te₄ due to the intrinsically broken time-reversal symmetry and the coherent dressing of an unequal number of particle- and hole-like bands.