Topological insulators are bulk insulators with a metallic surface which can be described, in the simplest case, by a single Dirac fermion. What are the properties of this metallic state when the surface is curved, such as in a cylindrical wire? How are these properties revealed in experiments, in particular in quantum transport? Are there phenomena unique to this system?

The metallic surface of a topological insulator nanowire turns out to be gapped. This is an effect of the Dirac fermion's non-trivial Berry phase as it winds around the cylindrical surface. A magnetic flux along the length of the wire can cancel this Berry phase and close the gap, thereby giving rise to the presence of a perfectly transmitted mode. This leads to various characteristic transport phenomena in these wires, such as magneto-conductance oscillations with period h/e, and a distinct peak in the supercurrent in a Josephson junction setup.

For further reading see:

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