Electric field-induced clustering in nanocomposite films of highly polarizable inclusions

TL;DR

This study investigates how highly polarizable inclusions in nanocomposite films self-organize under strong electric fields, revealing unexpected counter-polarization effects and diverse equilibrium structures with potential applications in sensing and plasmonics.

Contribution

It demonstrates the emergence of counter-polarization and complex structures in nanocomposites under high electric fields, a phenomenon not previously reported.

Findings

Counter-polarization occurs at high electric fields.

Diverse equilibrium structures including clusters and demixed states.

Guidance for controlling nanocomposite properties in applications.

Abstract

A nanocomposite film containing highly polarizable inclusions in a fluid background is explored when an external electric field is applied perpendicular to the planar film. For small electric fields, the induced dipole moments of the inclusions are all polarized in field direction, resulting in a mutual repulsion between the inclusions. Here we show that this becomes qualitatively different for high fields: the total system self-organizes into a state which contains both polarizations, parallel and antiparallel to the external field such that a fraction of the inclusions is counter-polarized to the electric field direction. We attribute this unexpected counter-polarization to the presence of neighboring dipoles which are highly polarized and locally revert the direction of the total electric field. Since dipoles with opposite moments are attractive, the system shows a wealth of novel equilibrium structures for varied inclusion density and electric field strength. These include fluids and solids with homogeneous polarizations as well as equilibrium clusters and demixed states with two different polarization signatures. Based on computer simulations of a linearized polarization model, our results can guide the control of nanocomposites for various applications, including sensing external fields, directing light within plasmonic materials, and controlling the functionality of biological membranes.