Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses

TL;DR

This study explores how low-frequency vibrational modes in colloidal glasses relate to particle rearrangements, revealing that these modes are spatially correlated with rearrangements in a thermal system.

Contribution

It demonstrates a correlation between low-frequency vibrational modes and particle rearrangements in colloidal glasses, using experimental measurements of the vibrational spectrum.

Findings

Low-frequency quasi-localized phonon modes are correlated with rearrangements.

Rearrangements are induced by small reductions in packing fraction.

Vibrational modes can predict regions prone to rearrangement.

Abstract

We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles which readily permit variation of sample packing fraction. At each packing fraction, the particle displacement covariance matrix is measured and used to extract the vibrational spectrum of the "shadow" colloidal glass (i.e., the particle network with the same geometry and interactions as the sample colloid but absent damping). Rearrangements are induced by successive, small reductions in packing fraction. The experimental results suggest that low-frequency quasi-localized phonon modes in colloidal glasses, i.e., modes that present low energy barriers for system rearrangements, are spatially correlated with rearrangements in this thermal system.