Transport in Topological Insulators

Topological Insulators are materials where the band-structure has a bulk band-gap but unusual quantum states are expected to exist at the surface. These so-called topological surface states appear as a result of a role switching between the conduction and valence bands across an interface. The surface states are characterized by a linear dispersion, similar to graphene, but are topologically protected due to underlying symmetries of the bulk band-structure.

Some of the most interesting predictions about topological insulators arise when considering their interface to superconductors. Under fine-tuned conditions, the interface is expected to host quantum states called “Majorana Bound States”, which are characterized by non-Abelian statistics. These states are one of the holy-grails of condensed matter physics, since they may form the foundation to fault-tolerant quantum computation schemes.

We study the properties of the topological surface states using low-temperature electronic transport measurements. We use the topological insulator Bi2Se3 which we synthesize by melting the constituent components in a heated quartz tube, and use electron beam lithography to contact exfoliated flakes – similar to the technique used for graphene devices.