Anisotropy in the helicity modulus of a 3D XY-model: application to YBCO

TL;DR

This study uses Monte Carlo simulations to analyze the anisotropic helicity moduli in a 3D XY-model of YBCO, revealing discrepancies with experimental data and suggesting classical phase fluctuations alone are insufficient.

Contribution

It provides the first Monte Carlo analysis of anisotropic helicity moduli in a 3D XY-model for YBCO, highlighting limitations of classical phase fluctuation models.

Findings

Both ab-plane and c-axis helicity moduli vary linearly with temperature at low T.

The c-axis helicity modulus results disagree with experimental data.

Classical phase fluctuations alone cannot explain YBCO's c-axis electrodynamics.

Abstract

We present a Monte Carlo study of the helicity moduli of an anisotropic classical three-dimensional (3D) XY-model of YBCO in superconducting state. It is found that both the ab-plane and the c-axis helicity moduli, which are proportional to the inverse square of the corresponding magnetic field penetration depth, vary linearly with temperature at low temperatures. The result for the c-axis helicity modulus is in disagreement with the experiments on high quality samples of YBCO. Thus we conclude that purely classical phase fluctuations of the superconducting order parameter cannot account for the observed c-axis electrodynamics of YBCO.