Defect Motion and Lattice Pinning Barrier in Josephson-Junction Ladders

TL;DR

This paper investigates the movement of domain wall defects in a frustrated Josephson-junction ladder, combining analytical calculations and numerical simulations to understand the energy barriers and dynamics involved.

Contribution

It provides the first analytical calculation of the defect motion barrier and extensive numerical analysis of defect dynamics across different system sizes.

Findings

Energy barrier E_B=0.1827 in large systems

Coherent defect motion observed in large systems

Analytical and numerical methods complement each other

Abstract

We study motion of domain wall defects in a fully frustrated Josephson-unction ladder system, driven by small applied currents. For small system sizes, the energy barrier E_B to the defect motion is computed analytically via symmetry and topological considerations. More generally, we perform numerical simulations directly on the equations of motion, based on the resistively-shunted junction model, to study the dynamics of defects, varying the system size. Coherent motion of domain walls is observed for large system sizes. In the thermodynamical limit, we find E_B=0.1827 in units of the Josephson coupling energy.