Unscreened universality class for superconductors with columnar disorder

TL;DR

This study reveals a new universality class for the vortex line phase transition in high-temperature superconductors with columnar defects under weak screening, characterized by distinct critical exponents and anisotropic scaling.

Contribution

It introduces the critical behavior of vortex lines with weak screening, showing a different universality class from the strongly screened case, supported by Monte Carlo simulations.

Findings

Identifies a new universality class with unique critical exponents.

Shows anisotropic scaling with a nontrivial anisotropy exponent.

Finds exponents similar to experimental results on YBCO superconductors.

Abstract

The phase transition in a model for vortex lines in high temperature superconductors with columnar defects, i.e., linearly correlated quenched random disorder, is studied with finite size scaling and Monte Carlo simulations. Previous studies of critical properties have mainly focused on the limit of strongly screened vortex line interactions. Here the opposite limit of weak screening is considered. The simulation results provide evidence for a new universality class, with new critical exponents that differ from the case of strong screening of the vortex interaction. In particular, scaling is anisotropic and characterized by a nontrivial value of the anisotropy exponent $\zeta=\nu_\parallel/\nu_\perp$. The exponents we find, $\zeta = 1.25 \pm 0.1, \nu_\perp=1.0 \pm 0.1, z = 1.95 \pm 0.1$, are similar to certain experimental results on YBCO.