Giant Colloidal Diffusivity on Corrugated Optical Vortices

TL;DR

This study reveals that colloidal particles in corrugated optical vortices exhibit significantly enhanced diffusivity, with their motion characterized by a linear diffusion law despite intermittent trapping and running states.

Contribution

It demonstrates the giant enhancement of colloidal diffusivity in corrugated optical vortices and characterizes the underlying dynamical switching behavior.

Findings

Effective diffusion coefficient is over 100 times larger than in free diffusion.

Particles alternate between free circulation and trapping in potential minima.

Diffusive behavior follows a linear Einstein-like law despite complex dynamics.

Abstract

A single colloidal sphere circulating around a periodically modulated optical vortex trap can enter a dynamical state in which it intermittently alternates between freely running around the ring-like optical vortex and becoming trapped in local potential energy minima. Velocity fluctuations in this randomly switching state still are characterized by a linear Einstein-like diffusion law, but with an effective diffusion coefficient that is enhanced by more than two orders of magnitude.