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Aharon Kapitulnik - Stanford University, USA

The magnetic field tuned superconductor (metal) to insulator transition


We combine measurements of the longitudinal and Hall resistivities of disordered two dimensional amorphous films to study the magnetic-field tuned superconductor to insulator transition (SIT) in the zero-temperature limit. We distinguish two different regimes for this transition. For weak disorder, intervening "metallic phases” with electron-hole symmetry character emerge above fields that are much smaller than the critical field. For strong disorder, a true superconductor to insulator transition is found, which is characterized by strongly inhomogeneous state. We find that in this regime the transition exhibits signatures of self-duality, and separates the superconducting state from a “Hall-insulator” phase. A higher characteristic magnetic field at which the Hall resistance is T independent marks a crossover to a Fermi-insulator, at which point the Hall resistance reaches the “canonical value” = H/nec. We also highlight a profound analogy between the magnetic-field tuned SIT and quantum-Hall liquid to insulator transitions.

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