Experimental evidence for a collective insulating state in two-dimensional superconductors

Phys Rev Lett. 2005 Jan 14;94(1):017003. doi: 10.1103/PhysRevLett.94.017003. Epub 2005 Jan 12.

Abstract

We present the results of an experimental study of the current-voltage characteristics in a strong magnetic field (B) of disordered, superconducting, thin films of amorphous indium oxide. As the B strength is increased superconductivity degrades, until a critical field (B(c)) where the system is forced into an insulating state. We show that the differential conductance measured in the insulating phase vanishes abruptly below a well-defined temperature, resulting in a clear threshold for conduction. Our results indicate that a new collective state emerges in two-dimensional superconductors at high B.