Low energy modes and Debye behaviour in a colloidal crystal

TL;DR

This study investigates the vibrational properties of a colloidal crystal, revealing deviations from Debye behavior in the density of states, supported by experiments, simulations, and an effective theoretical model.

Contribution

It introduces an effective theory for mode projections that explains the observed vibrational spectrum in a colloidal crystal.

Findings

Density of states deviates from Debye predictions

Experimental and simulation data are consistent with the effective theory

Low energy modes exhibit non-Debye behavior

Abstract

We study the vibrational spectrum and the low energy modes of a three dimensional colloidal crystal using confocal microscopy. This is done in a two-dimensional cut through a three-dimensional crystal. We find that the observed density of states is incompatible with the standard Debye form in either two or three dimensions. These results are confirmed by numerical simulations. We show that an effective theory for the projections of the modes onto the two-dimensional cut describes the experimental and simulation data in a satisfactory way.