Flux-noise spectra around the Kosterlitz-Thouless transition for two-dimensional superconductors

TL;DR

This paper investigates flux-noise spectra near the Kosterlitz-Thouless transition in 2D superconductors using simulations, clarifying how coil distance affects measurements and identifying experimental features.

Contribution

It provides a detailed simulation study of flux-noise spectra around the transition, highlighting the impact of coil distance and clarifying the relation between impedance and noise in different regimes.

Findings

Distinct flux-noise features for large and small coil distances

Clarification of impedance-noise relation in the large-distance limit

Identification of experimental signatures of the transition

Abstract

The flux-noise spectra around the Kosterlitz-Thouless transition are obtained from simulations of the two-dimensional resistively shunted junction model. In particular the dependence on the distance $d$ between the pick-up coil and the sample is investigated. The typical experimental situation corresponds to the large-$d$ limit and a simple relation valid in this limit between the complex impedance and the noise spectra is clarified. Features, which distinguish between the large- and small-$d$ limit, are identified and the possibility of observing these features in experiments is discussed.