Scanning probe studies on the surface of bismuth selenide

Topological insulators are an exciting material that are insulating in the bulk, but have a metallic surface state where spin and momentum are locked perpendicular to each other by strong spin orbit coupling. The simplest topological insulator, Bi2Se3, has a band gap of ∼0.3 eV and a single Dirac cone, a state where energy and momentum are linearly related, in the gap. This special state is protected against scattering and small perturbations by time reversal symmetry. Before any of the exotic effects predicted to be present in this material can be fully realized, it is important to know what other electronic effects coexist with the topological state on the surface of the material. To that end, I employed scanning tunneling microscopy on the surface of Bi2Se3 far from defect states. I probed the interplay of bulk electrons with the Dirac cone that adds additional states. I also show that the Dirac cone can coexist with a two-dimensional electron gas, although the amplitude is potentially reduced.