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Jeudi 23 Avril 2015 14h
Aharon Kapitulnik , Stanford University
Amphi Holweck, Esc C, 1ème etage
Duality and an emerging Hall insulator phase and duality near the magnetic-field tuned superconductor-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.