Interview for Faculty Position

3D topological insulators and the quest for surface states

Nicholas P. Butch

Center for Nanophysics and Advanced Materials
Department of Physics
University of Maryland

In theory, three dimensional topological insulators are bulk insulators with two dimensional metallic surfaces that have a Dirac-like dispersion and a helical spin-momentum correspondence. Experimental confirmation of these states primarily comes from surface-sensitive measurements. In contrast, these surface states have proven to be very difficult to reliably study via bulk electrical transport measurements, despite the notion of “topological protection” that is a unique robustness of the surface conduction against disorder. In order to utilize these materials in possible future applications like quantum computing, it will be necessary to demonstrate that the surfaces are really good quality metals.

At the University of Maryland, we have synthesized single crystals of Bi₂Se₃ with exceptionally low bulk carrier density and high mobility, which has been uniquely achieved without chemical substitution. I will assess the quality of our current evidence for bulk topological surface transport and offer a perspective on the experimental state of the field.