Low-frequency vibrations of soft colloidal glasses

TL;DR

This study investigates low-frequency vibrational modes in soft colloidal glasses near the jamming transition, revealing similarities to atomic glasses and identifying a shifting boson peak with compression.

Contribution

It introduces experimental measurements of vibrational properties in colloidal glasses, connecting real systems to theoretical zero-temperature models.

Findings

Vibrational spectrum resembles that of idealized sphere models.

Presence of a boson peak at low frequency.

Peak shifts to higher frequency with increased packing.

Abstract

We conduct experiments on two-dimensional packings of colloidal thermosensitive hydrogel particles whose packing fraction can be tuned above the jamming transition by varying the temperature. By measuring displacement correlations between particles, we extract the vibrational properties of a corresponding "shadow" system with the same configuration and interactions, but for which the dynamics of the particles are undamped. The vibrational spectrum and the nature of the modes are very similar to those predicted for zero-temperature idealized sphere models and found in atomic and molecular glasses; there is a boson peak at low frequency that shifts to higher frequency as the system is compressed above the jamming transition.