Directional Locking Effects and Dynamics for Particles Driven Through a Colloidal Lattice

TL;DR

This study explores how a single colloidal particle's driven motion through a deformable colloidal lattice exhibits complex locking behaviors, velocity anomalies, and potential for particle segregation, with implications for understanding driven disordered systems.

Contribution

It reveals the rich dynamical locking phenomena and velocity anomalies in a deformable colloidal lattice, extending prior fixed substrate models to more realistic, deformable systems.

Findings

Locking to lattice symmetry directions occurs with velocity anomalies.

Transverse forces can increase or decrease drag depending on drive angle.

Enhanced locking and lattice distortion happen with increased particle-lattice interaction.

Abstract

We examine the dynamics of a single colloidal particle driven through a colloidal lattice which can distort in response to the driven particle. We find a remarkably rich variety of dynamical locking phenomena as we vary the angle of the applied drive with respect to the orientation of the colloidal lattice. When the driven colloid locks to certain lattice symmetry directions, its motion is not necessarily aligned with the drive. Applying a transverse force to the driven particle can result in either increased or decreased drag in the driving direction, depending on the angle of the drive. The dynamical locking produces anomalies in both the longitudinal and the transverse velocity vs driving force curves, including steps and regimes of negative differential resistance. As the interaction of the driven particle with the surrounding lattice increases, significant distortion or dislocations in the surrounding media occur, and as a result the directional locking is enhanced. We compare these results to those obtained for driving particles over fixed substrates, and show that a far richer variety of behaviors occurs when the underlying lattice is allowed to distort. We discuss how this system can be used for particle species segregation when the onset of different locking angles occurs at different drives for varied particle sizes. We also show that the most pronounced locking phases should be observable at temperatures up to the melting transition of the colloidal lattice.