Statistics of non-affine defect precursors: tailoring defect densities in colloidal crystals using external fields

TL;DR

This paper investigates how non-affine fluctuations in colloidal crystals serve as precursors to defect formation and proposes external fields to control defect densities, with experimental verification feasible using holographic techniques.

Contribution

It introduces a method to manipulate defect densities in colloidal crystals by applying external fields conjugate to non-affinity, based on analyzing non-affine fluctuations as defect precursors.

Findings

Non-affine fluctuations act as precursors for defect nucleation.

External fields can modify defect probabilities.

Experimental methods are proposed for verification.

Abstract

Coarse-graining atomic displacements in a solid produces both local affine strains and "non-affine" fluctuations. Here we study the equilibrium dynamics of these coarse grained quantities to obtain space-time dependent correlation functions. We show how a subset of these thermally excited, non-affine fluctuations act as precursors for the nucleation of lattice defects and suggest how defect probabilities may be altered by an {\it experimentally realisable} "external" field conjugate to the global non-affinity parameter. Our results are amenable to verification in experiments on colloidal crystals using commonly available holographic laser tweezer and video microscopy techniques, and may lead to simple ways of controlling the defect density of a colloidal solid.