Dynamic ordering and frustration of confined vortex rows studied by mode-locking experiments

TL;DR

This study investigates how confined vortex rows in mesoscopic channels behave under different magnetic fields using mode-locking experiments, revealing how their structure, pinning, and flow dynamics evolve with field conditions.

Contribution

It provides new insights into the dynamic ordering and frustration of vortex rows, including quantifying pinning and ordering velocities and their dependence on magnetic field mismatch.

Findings

Maximum coherent motion occurs at matching fields with low pinning.

Mismatch fields increase pinning strength and ordering velocity.

The relation $f_c \,\propto\, f_p^2$ supports existing dynamic ordering theories.

Abstract

The flow properties of confined vortex matter driven through disordered mesoscopic channels are investigated by mode locking (ML) experiments. The observed ML effects allow to trace the evolution of both the structure and the number of confined rows and their match to the channel width as function of magnetic field. From a detailed analysis of the ML behavior for the case of 3-rows we obtain ({\it i}) the pinning frequency $f_p$, ({\it ii}) the onset frequency $f_c$ for ML ($\propto$ ordering velocity) and ({\it iii}) the fraction $L_{ML}/L$ of coherently moving 3-row regions in the channel. The field dependence of these quantities shows that, at matching, where $L_{ML}$ is maximum, the pinning strength is small and the ordering velocity is low, while at mismatch, where $L_{ML}$ is small, both the pinning force and the ordering velocity are enhanced. Further, we find that $f_c \propto f_p^2$, consistent with the dynamic ordering theory of Koshelev and Vinokur. The microscopic nature of the flow and the ordering phenomena will also be discussed.