Rotational Jamming of Plasmonic Optical Matter Driven by Chiral Light

TL;DR

This paper investigates how plasmonic optical matter driven by chiral light can undergo rotational jamming transitions, revealing the relationship between assembly symmetry and its ability to sustain rotation, with implications for optical micromachines.

Contribution

It introduces the concept of rotational jamming in plasmonic optical matter and demonstrates how assembly symmetry affects the ability to harness spin angular momentum for rotation.

Findings

Stable hexagonal and triangular assemblies efficiently harness SAM.

Growth of assemblies leads to disruption and transition to fluid-like states.

Rotation ceases as structural order diminishes, indicating jamming.

Abstract

Plasmonic Optical matter (OM), composed of optically bound metallic particles, can be rotated by transferring the spin angular momentum (SAM) of chiral light to the assembly. Rotating OM is a promising platform for optical micromachines, with potential applications in plasmofluidics and soft robotics. Understanding the dynamic states of such Brownian, micro-mechanical systems is a relevant issue. One key problem is understanding kinetic jamming and clogging. Studies of driven multiparticle systems have revealed that under suboptimal driving, the systems can stop moving, showing jamming transitions. It is important to identify dynamic regimes where crowding competes with driving and is susceptible to jamming in the context of optical micromachines. Through experiments supported by numerical simulations, we reveal assemblies with well-defined hexagonal or triangular symmetry that efficiently harness the SAM of incident chiral light, resulting in stable rotation. However, as the plasmonic-particle assembly grows and its dimensions approach the beam waist, new particles can disrupt this order. This causes a transition to a fluid-like state with less-defined symmetry, correlated with a significant reduction in transferred torque, causing rotation to stagnate or cease. We suggest this behaviour is analogous to a rotational jamming transition, where the rotational motion is arrested. Our findings establish a clear relationship between the structural symmetry of the OM assembly and its ability to harness SAM, providing new insights into controlling chiral light-matter interactions and offering a novel platform for studying jamming transitions.