Renormalization Group Study of the Intrinsic Finite Size Effect in 2D Superconductors

TL;DR

This paper investigates how the finite 2D magnetic penetration depth causes intrinsic finite size effects in thin-film superconductors, using a renormalization group approach to analyze the 2D Yukawa gas model.

Contribution

It maps the 2D Yukawa gas to the massive sine-Gordon model and derives recursion relations to understand the relevance of the penetration depth parameter.

Findings

The 2D magnetic penetration depth is a relevant parameter affecting critical behavior.

Recursion relations for the system's physical quantities are derived and solved.

Finite size effects are less prominent in experiments due to the influence of current.

Abstract

Vortices in a thin-film superconductor interact logarithmically out to a distance on the order of the two-dimensional (2D) magnetic penetration depth $\lambda_\perp$, at which point the interaction approaches a constant. Thus, because of the finite $\lambda_\perp$, the system exhibits what amounts to an {\it intrinsic} finite size effect. It is not described by the 2D Coulomb gas but rather by the 2D Yukawa gas (2DYG). To study the critical behavior of the 2DYG, we map the 2DYG to the massive sine-Gordon model and then perform a renormalization group study to derive the recursion relations and to verify that $\lambda_\perp$ is a relevant parameter. We solve the recursion relations to study important physical quantities for this system including the renormalized stiffness constant and the correlation length. We also address the effect of current on this system to explain why finite size effects are not more prevalent in experiments given that the 2D magnetic penetration depth is a relevant parameter.