Please join us for a CME Seminar presented by Professor James Valles from Brown University as he shares his research on "Tuning Gauge Disorder at the Superconductor to Insulator Transition".
Abstract
Although quantum phase transitions can occur in perfectly uniform systems, they usually do not. Real materials contain impurities or lattice imperfections or inhomogeneities that render them different from model Hamiltonians. Comparisons of experiments with theory require understanding the influence of such disorder.
In this talk, I will describe our experimental system that allows us to tune disorder at a superconductor to insulator transition (SIT). We employ ultrathin superconducting films patterned with an approximately triangular array of holes in a perpendicular magnetic field. These films can be driven through a series of superconductor to insulator transitions with increasing magnetic field. The SITs occur as the number of flux quanta per unit cell of the array cycles from integer to half integer values. Random geometric variations in the unit cell areas create random variations in the number of flux quanta per unit cell. This flux or gauge disorder grows proportional to the applied magnetic field. We have investigated how flux disorder influences the quantum critical transport at the SIT and demonstrated that it can produce a new disorder tuned quantum phase transition: a Random Gauge Field Tuned SIT.
