Driven Probe Particle Dynamics in a Bubble Forming System

TL;DR

This study numerically investigates the complex dynamics of a driven probe particle in a bubble-forming particle assembly, revealing multiple flow regimes, dynamic transitions, and their signatures in velocity and drag measurements.

Contribution

It introduces a detailed dynamic phase diagram for probe particle motion in a bubble state with varied interactions, sizes, and densities, highlighting new flow regimes and transition signatures.

Findings

Identification of elastic, plastic, breakthrough, and high-speed regimes.

Observation of velocity-force jumps and velocity fluctuation signatures.

Mapping of the dynamic phase diagram across parameters.

Abstract

We numerically examine the dynamics of a probe particle driven at a constant force through an assembly of particles with competing long-range repulsion and short-range attraction that forms a bubble or stripe state. In the bubble regime, we identify several distinct types of motion, including an elastic or pinned regime where the probe particle remains inside a bubble and drags all other bubbles with it. There is also a plastic bubble phase where the bubble in which the probe particle is trapped is able to move past the adjacent bubbles. At larger drives, there is a breakthrough regime where the probe particle jumps from bubble to bubble, and in some cases, can induce correlated rotations or plastic rearrangements of the particles within the bubbles. At the highest drives, the probe particle moves sufficiently rapidly that the background particles undergo only small distortions. The distinctive dynamic flow states and the transitions between them are accompanied by signatures in the effective drag on the driven particle, jumps in the velocity-force curves, and changes in the time-dependent velocity fluctuations. We map the dynamic phase diagram for this system for varied interaction lengths, bubble sizes, and densities.