Dissipative phases across the superconductor-to-insulator transition

Abstract

Competing phenomena in low dimensional systems can generate exotic electronic phases, either through symmetry breaking or a non-trivial topology. In two-dimensional (2D) systems, the interplay between superfluidity, disorder and repulsive interactions is especially fruitful in this respect although both the exact nature of the phases and the microscopic processes at play are still open questions. In particular, in 2D, once superconductivity is destroyed by disorder, an insulating ground state is expected to emerge, as a result of a direct superconductor-to-insulator quantum phase transition. In such systems, no metallic state is theoretically expected to survive to the slightest disorder. Here we map out the phase diagram of amorphous NbSi thin films as functions of disorder and film thickness, with two metallic phases in between the superconducting and insulating ones. These two dissipative states, defined by a resistance which extrapolates to a finite value in the zero temperature limit, each bear a specific dependence on disorder. We argue that they originate from an inhomogeneous destruction of superconductivity, even if the system is morphologically homogeneous. Our results suggest that superconducting fluctuations can favor metallic states that would not otherwise exist.

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• Niobium nitride thin films for very low temperature resistive thermometry
• Anomalous metals: from "failed superconductor" to "failed insulator"
• Superconducting MoSi nanowires
• Robust anomalous metallic states and vestiges of self duality in two-dimensional granular In-InOx composites
• Overactivated transport in the localized phase of the superconductor-insulator transition
• Origin of Topological Order in a Cooper Pair Insulator
• Vortex Variable Range Hopping in a Conventional Superconducting Film
• Voltage-tuned anomalous-metal to metal transition in hybrid Josephson junction arrays
• Non-equilibrium restoration of duality symmetry in the vicinity of the superconductor-insulator transition
• Sample-based calibration for cryogenic broadband microwave reflectometry measurements