Non-Equilibrium Strongly Hyperuniform Fluids of Circle Active Particles with Large Local Density Fluctuations

TL;DR

This paper introduces a novel non-equilibrium fluid of chiral active particles exhibiting strong hyperuniformity, characterized by suppressed long-wavelength density fluctuations despite large local fluctuations, achieved through motility-induced microphase separation.

Contribution

It presents the discovery of a new hyperuniform fluid of circle active particles and develops a dynamic mean-field theory to explain its density fluctuation behavior.

Findings

Large local density fluctuations due to microphase separation.

Global hyperuniformity at large scales from diffusive and noise effects.

Identification of a length scale set by particle circular motion.

Abstract

Disordered hyperuniform structures are an exotic state of matter having vanishing long-wavelength density fluctuations similar to perfect crystals but without long-range order. Although its importance in materials science has been brought to the fore in past decades, the rational design of experimentally realizable disordered strongly hyperuniform microstructures remains challenging. Here we find a new type of non-equilibrium fluid with strong hyperuniformity in two-dimensional systems of chiral active particles, where particles perform independent circular motions of the radius R with the same handedness. This new hyperuniform fluid features a special length scale, i.e., the diameter of the circular trajectory of particles, below which large density fluctuations are observed. By developing a dynamic mean-field theory, we show that the large local density fluctuations can be explained as a motility-induced microphase separation, while the Fickian diffusion at large length scales and local center-of-mass-conserved noises are responsible for the global hyperuniformity.