Title: The Superconducting Insulator
Abstract: Many two-dimensional superconductors undergo a transition to an electric insulator as a function of different parameters such as thickness, disorder, magnetic field, chemical composition etc. This superconductor-insulator-transition has been an active area of research for the last few decades, nevertheless, some fundamental questions remain unsolved. In particular, the nature of the insulating phase, which shows unconventional transport properties, is unclear. One exciting scenario suggests that this phase incorporates superconducting fluctuating islands embedded in an insulating matrix, making it exceptional and unsimilar to any conventional superconductor or insulator.
In this colloquium I will present findings, obtained by our group as well by others, demonstrating the uniqueness of this “superconducting insulator”. These include a disorder enhanced superconducting energy gap, a novel proximity effect, unusual vortex motion and excess superconducting specific heat in the insulator. These results provide important insight into the physics governed by the interplay between disorder and two-dimensional superconductivity.