Irreversibility, Mechanical Entanglement and Thermal Melting in Superconducting Vortex Crystals with Point Impurities

TL;DR

This paper models how vortex lines in high Tc superconductors become irreversible and entangled due to disorder and thermal effects, aligning well with experimental observations.

Contribution

It introduces a simplified cage model combining Flory arguments and directed polymer results to estimate vortex behavior under disorder and temperature.

Findings

Irreversibility and entanglement depend nonmonotonically on disorder strength.

The model's predictions agree qualitatively with recent experimental data.

Thermal melting is influenced by point impurities and thermal fluctuations.

Abstract

We discuss the onset of irreversibility and entanglement of vortex lines in high Tc superconductors due to point disorder and thermal fluctuations using a simplified cage model. A combination of Flory arguments, known results from directed polymers in random media, and a Lindemann criterion are used to estimate the field and temperature dependence of irreversibility, mechanical entanglement and thermal melting. The qualitative features of this dependence, including its nonmonotonicity when disorder is sufficiently strong, are in good agreement with recent experiments.