Hybridization-induced gapped and gapless states on the surface of magnetic topological insulators

The Mn-Bi-Te family of materials hold promise for realizing the quantum anomalous Hall effect, provided that the topological surface states are gapped by magnetic order. However, previous ARPES measurements have revealed gapless surface Dirac cones for all Mn-Bi-Te antiferromagnetic members. Here, combining ARPES, DFT and tight-binding simulations, the authors find out that the gapless surface Dirac cones result from hybridization between surface and bulk states. This hybridization gives the surface states bulk distribution, with much reduced effective magnetic moment, and thus not sensitive to antiferromagnetic order.