Alternating Superconductor--Insulator Transport Characteristics in a Quantum Vortex Chain

TL;DR

This paper models the transport properties of a quantum vortex chain in a superconducting device near a superconductor-insulator transition, revealing oscillatory magnetoresistance and distinct I-V behaviors in different phases.

Contribution

It introduces a theoretical model mapping vortex dynamics to 1D fermions, predicting a quantum phase transition and explaining experimental oscillations in magnetoresistance.

Findings

Magnetoresistance R(B) shows oscillations similar to experiments.

I-V characteristics differ markedly between superconducting and insulating phases.

A quantum phase transition of Ising type occurs at specific vortex fillings.

Abstract

Experimental studies of magnetoresistance in thin superconducting strips subject to a perpendicular magnetic field B exhibit a multitude of transitions, from superconductor to insulator and vice versa alternately. Motivated by this observation, we study a theoretical model for the transport properties of a ladder--like superconducting device close to a superconductor--insulator transition. In this regime, strong quantum fluctuations dominate the dynamics of the vortex chain forming along the device. Utilizing a mapping of the vortex system at low energies to one-dimensional (1D) Fermions at a chemical potential dictated by B, we find that a quantum phase transition of the Ising type occurs at critical values of the vortex filling, from a superconducting phase near integer filling to an insulator near 1/2-filling. The current--voltage (I-V) characteristics of the weakly disordered device in the presence of a d.c. current bias I is evaluated, and investigated as a function of B, I, the temperature T and the disorder strength. In the Ohmic regime (I/e << T), the resulting magnetoresistance R(B) exhibits oscillations similar to the experimental observation. More generally, we find that the I-V characteristics of the system manifests a dramatically distinct behavior in the superconducting and insulating regimes.