Weakly Protected 1D Topological Step Edge States at the Surface of a 3D Topological Insulator

Topological insulators in the Bi₂Se₃ family manifest helical Dirac surface states that span the topologically ordered bulk band gap. Recent scanning tunneling microscopy measurements have discovered in-gap states at step edges in the bulk band gap of Bi₂Se₃ and Bi₂Te₃, possibly caused by a band bending-like phenomenon. We use numerical simulations of a topological insulator surface to explore the phenomenology of edge state formation at the single-quintuple-layer step defects found ubiquitously on these materials. The modeled one-dimensional edge states are found to exhibit a protected topological connection to the two-dimensional surface state Dirac point. I will discuss the emergence and physical significance of this topologically connected 1D edge state, as well as how it evolves under broken symmetries and disorder.