Dynamic mode locking in a driven colloidal system: experiments and theory

TL;DR

This study investigates how a colloidal particle's motion synchronizes into discrete modes under a modulated drive over a sinusoidal potential, combining experiments, theory, and simulations to map the conditions for mode locking.

Contribution

It provides a comprehensive analysis of mode locking phenomena in colloidal systems, integrating experimental results with theoretical and simulation models to extend understanding of dynamic synchronization.

Findings

Mode locked steps appear over a range of velocities.

Amplitude and frequency influence the locking behavior.

State diagrams map the locked modes in parameter space.

Abstract

In this article we examine the dynamics of a colloidal particle driven by a modulated force over a sinusoidal optical potential energy landscape. Coupling between the competing frequencies of the modulated drive and that of particle motion over the periodic landscape leads to synchronisation of particle motion into discrete modes. This synchronisation manifests as steps in the average particle velocity, with mode locked steps covering a range of average driving velocities. The amplitude and frequency dependence of the steps are considered, and compared to results from analytic theory, Langevin Dynamics simulations, and Dynamic Density Functional Theory. Furthermore, the critical driving velocity is studied, and simulation used to extend the range of conditions accessible in experiments alone. Finally, state diagrams from experiment, simulation, and theory are used to show the extent of the dynamically locked modes in two dimensions, as a function of both the amplitude and frequency of the modulated drive.