Pattern Switching and Polarizability for Colloids in Optical Trap Arrays

TL;DR

This paper demonstrates how colloidal crystals in optical trap arrays can rapidly switch patterns and polarize under external fields, revealing new dynamic behaviors with potential applications in photonic devices.

Contribution

It introduces a novel mechanism for pattern switching and polarization in colloidal systems interacting with periodic substrates and external fields.

Findings

Rapid pattern switching in colloidal crystals observed.

Martensitic-like symmetry transitions identified.

Creation of polarized states with rotating director fields.

Abstract

We show that colloidal molecular crystal states interacting with a periodic substrate, such as an optical trap array, and a rotating external field can undergo a rapid pattern switching in which the orientation of the crystal changes. In some cases, a martensitic-like symmetry switching occurs. It is also possible to create a polarized state where the colloids in each substrate minima develop a director field which smoothly rotates with the external drive, similar to liquid crystal behavior. These results open the possibility for creating novel types of devices using photonic band gap materials, and should be generalizable to a variety of other condensed matter systems with multiple particle trapping.