Increasing the density melts ultrasoft colloidal glasses

TL;DR

This paper combines theory and simulations to reveal a re-entrant glass transition in ultrasoft colloids, where increasing density first forms and then melts the glass, highlighting the unique effects of particle softness.

Contribution

It introduces a combined theoretical and simulation approach to demonstrate re-entrant glass melting in ultrasoft colloids due to particle softness.

Findings

Re-entrant fluid-glass transition observed at high densities.

Glass melts upon further compression due to particle softness.

Theoretical predictions confirmed by numerical simulations.

Abstract

We use theory and simulations to investigate the existence of amorphous glassy states in ultrasoft colloids. We combine the hyper-netted chain approximation with mode-coupling theory to study the dynamic phase diagram of soft repulsive spheres interacting with a Hertzian potential, focusing on low temperatures and large densities. At constant temperature, we find that an amorphous glassy state is entered upon compression, as in colloidal hard spheres, but the glass unexpectedly melts when density increases further. We attribute this re-entrant fluid-glass transition to particle softness, and correlate this behaviour to previously reported anomalies in soft systems, thus emphasizing its generality. The predicted fluid-glass-fluid sequence is confirmed numerically.