Dissipation-driven quantum phase transition in superconductor-graphene systems

TL;DR

This paper investigates how coupling Josephson junctions to graphene can induce a dissipation-driven quantum phase transition, enabling control over superconductivity and insulating states via gate-tunable charge fluctuations.

Contribution

It develops a theoretical model describing dissipation-driven superconductor-insulator transition in Josephson junction arrays coupled to graphene, highlighting the role of graphene's Fermi energy in controlling the transition.

Findings

Quantum phase transition scales exponentially with graphene's Fermi energy.

Coupling to graphene enhances charge fluctuations, promoting superconductivity.

The theory applies to 2D arrays and qualitatively to 1D systems.

Abstract

We show that a system of Josephson junctions coupled via low-resistance tunneling contacts to graphene substrate(s) may effectively operate as a current switching device. The effect is based on the dissipation-driven superconductor-to-insulator quantum phase transition, which happens due to the interplay of the Josephson effect and Coulomb blockade. Coupling to a graphene substrate with gapless excitations further enhances charge fluctuations favoring superconductivity. The effect is shown to scale exponentially with the Fermi energy in graphene, which can be controlled by the gate voltage. We develop a theory, which quantitatively describes the quantum phase transition in a two-dimensional Josephson junction array, but it is expected to provide a reliable qualitative description for one-dimensional systems as well. We argue that the local effect of dissipation-induced enhancement of superconductivity is very robust and a similar sharp crossover should be present in finite Josephson junction chains.