Critical Currents and Melting Temperature of a Two-dimensional Vortex Lattice with Periodic Pinning

TL;DR

This study investigates the critical currents and melting temperatures of a two-dimensional vortex lattice with periodic pinning, revealing higher critical currents and melting temperatures for hexagonal arrays and anisotropic effects influenced by temperature.

Contribution

It provides a comparative analysis of vortex behavior in hexagonal and Kagomé pinning arrays using molecular dynamics simulations, highlighting the impact of lattice geometry on critical currents and melting.

Findings

Hexagonal pinning yields higher critical currents.

Melting temperature is higher for hexagonal arrays.

Kagomé arrays exhibit multi-stage phase melting.

Abstract

The critical current and melting temperature of a vortex system are analyzed. Calculations are made for a two dimensional film at finite temperature with two kinds of periodic pinning: hexagonal and Kagom\'e. A transport current parallel and perpendicular to the main axis of the pinning arrays is applied and molecular dynamics simulations are used to calculate the vortex velocities to obtain the critical currents. The structure factor and displacements of vortices at zero transport current are used to obtain the melting temperature for both pinning arrays. The critical currents are higher for the hexagonal pinning lattice and anisotropic for both pinning arrays. This anisotropy is stronger with temperature for the hexagonal array. For the Kagom\'e pinning lattice, our analysis shows a multi stage phase melting; that is, as we increase the temperature, each different dynamic phase melts before reaching the melting temperature. Both the melting temperature and critical currents are larger for the hexagonal lattice, indicating the role for the interstitial vortices in decreasing the pinning strength.