Enhanced vortex pinning by a composite antidot lattice in a superconducting Pb film

TL;DR

This study demonstrates that a composite antidot lattice in a superconducting Pb film enhances vortex pinning, increases critical current, and expands the field range for superconductivity by trapping more flux quanta.

Contribution

Introduction of a composite antidot lattice with small antidots at cell centers to improve vortex pinning and critical current in superconducting films.

Findings

Composite antidot lattice traps more flux quanta per unit cell.

Enhanced critical current over a wider magnetic field range.

Stable vortex lattice patterns identified via simulations.

Abstract

The use of artificial defects is known to enhance the superconducting critical parameters of thin films. In the case of conventional superconductors, regular arrays of submicron holes (antidots) substantially increase the critical temperature Tc(H) and critical current Ic(H) for all fields. Using electrical transport measurements, we study the effect of placing an additional small antidot in the unit cell of the array. This composite antidot lattice consists of two interpenetrating antidot square arrays with a different antidot size and the same lattice period. The smaller antidots are located exactly at the centers of the cells of the array of large antidots. We show that the composite antidot lattice can trap a higher number of flux quanta per unit cell inside the antidots, compared to a reference antidot film without the additional small antidots in the center of the cells. As a consequence, the field range in which an enhanced critical current is observed is considerably expanded. Finally, the possible stable vortex lattice patterns at several matching fields are determined by molecular dynamics simulations.