Structural Tuning Magnetism and Topology in a Magnetic Topological Insulator

Abstract

Abstract To date, the most widely‐studied quantum anomalous Hall insulator (QAHI) platform is achieved by dilute doping of magnetic ions into thin films of the alloyed tetradymite topological insulator (TI) (Bi 1 − x Sb x ) 2 Te 3 (BST). In these films, long‐range magnetic ordering of the transition metal substituants opens an exchange gap Δ in the topological surface states, stabilizing spin‐polarized, dissipationless edge channels with a nonzero Chern number . The long‐range ordering of the spatially separated magnetic ions is itself mediated by electronic states in the host TI, leading to a sophisticated feedback between magnetic and electronic properties. Here, a study is presented on the electronic and magnetic response of a BST‐based QAHI system to structural tuning via hydrostatic pressure. A systematic closure of the topological gap under compressive strain is identified accompanied by a simultaneous enhancement in the magnetic ordering strength. Combining these experimental results with first‐principle calculations, structural deformation is identified as a strong tuning parameter to traverse a rich topological phase space and modify magnetism in the magnetically doped BST system.