Hyperuniform Density Distributions of Brownian Particles via Designer External Potentials

TL;DR

This paper analytically explores how external potentials can induce and control disordered hyperuniformity in Brownian particles at equilibrium, revealing conditions for achieving such states and the dynamics involved.

Contribution

It derives conditions on external potentials to produce hyperuniform density distributions of Brownian particles and analyzes the dynamics of their evolution towards equilibrium.

Findings

External potentials can be designed to induce hyperuniform states.

Thermal motions tend to enhance hyperuniformity.

Transient states show rapid local pattern formation.

Abstract

Disordered hyperuniformity (DHU) is a recently discovered novel state of many-body systems that is characterized by vanishing normalized infinite-wavelength density fluctuations similar to a perfect crystal, yet possesses an amorphous structure like a liquid or glass. Here we investigate equilibrium DHU states of Brownian particles induced by external potentials. In particular, we analytically derive sufficient conditions on the external potentials in order to achieve distinct classes of DHU density distributions of Brownian particles in thermal equilibrium, based on the stationary-state solutions of the corresponding Smoluchowski equation. We show for a wide spectrum of tight-binding potentials, the desirable DHU states of Brownian particles can be controlled and achieved by imposing proper hyperuniformity conditions on the potentials. Moreover, we find that thermal motions in these systems tend to enhance hyperuniformity. We also analyze the evolution dynamics of an initial density distribution (hyperuniform or non-hyperuniform) to the desirable equilibrium DHU state determined by the prescribed external potentials, which is shown to be coupled with the full spectra of the force fields associated with the imposed potentials. We find that although the transient density distribution can rapidly develop local patterns reminiscent of those in the equilibrium distribution, which is governed by the fast dynamics induced by the external potential, the overall distribution is still modulated by the initial density fluctuations which are relaxed through slow diffusive dynamics. Our study has implications for the fabrication of designer DHU materials.