Comment on ``Loss of Superconducting Phase Coherence in YBa_2Cu_3O_7 Films: Vortex-Loop Unbinding and Kosterlitz-Thouless Phenomena''

TL;DR

This paper critiques a previous interpretation of frequency-dependent conductance in YBa_2Cu_3O_7 films, arguing that the data align better with 2D vortex fluctuations rather than 3D vortex loop proliferation.

Contribution

It challenges the previous 3D vortex loop interpretation and supports the relevance of 2D vortex fluctuations in explaining the conductance data.

Findings

Data features inconsistent with 3D vortex loop model

Evidence supporting 2D vortex fluctuation phenomenology

Highlights partial decoupling of CuO_2-planes

Abstract

Recently, Kotzler et al. measured the frequency-dependent conductance for YBa_2Cu_3O_7 and interpreted their results as evidences that the decay of the superfluid density is caused by a 3D vortex loop proliferation mechanism and a dimensional crossover when the correlation length $\xi_c$ along the c axis becomes comparable to the sample thickness $d$ [PRL 87, 127005(2001)]. In this Comment, we show that the complex conductance data presented by Kotzler et al. have characteristic key features not compatible with their analysis, which are instead described by the existing phenomenology of 2D vortex fluctuation associated with a partial decoupling of CuO_2-planes.