Superconductor to Insulator Transition Tuned by Random Gauge Fields

TL;DR

This paper demonstrates that random gauge field disorder can induce a superconductor-insulator transition in a nano-patterned amorphous Bi array, providing a new experimental platform to study quantum phase transitions driven by gauge field disorder.

Contribution

It introduces a novel experimental method to control gauge field disorder and directly observe its effects on quantum phase transitions in a superconducting system.

Findings

Observation of superfluid bose glass to insulator transition at critical gauge disorder

Signatures of metallic transport near the critical point with resistance ~0.5 h/4e^2

Critical disorder depends on interisland coupling, matching theoretical predictions

Abstract

Typically the disorder that alters the interference of particle waves to produce Anderson localization is potential scattering from randomly placed impurities. Here we show that disorder in the form of random gauge fields that act directly on particle phases can also drive localization. We present evidence of a superfluid bose glass to insulator transition at a critical level of this gauge field disorder in a nano-patterned array of amorphous Bi islands. This transition shows signs of metallic transport near the critical point characterized by a resistance of order 0.5 h/4e^2 , indicative of a quantum phase transition. The critical disorder also depends on interisland coupling in agreement with recent Quantum Monte Carlo simulations. Finally, these experiments are uniquely connected to theory because they employ a method for controlling a disorder parameter that coincides directly with a term that appears in model Hamiltonians. This correspondence will enable further high fidelity comparisons between theoretical and experimental studies of disorder effects on quantum critical systems.