Disconnected Glass-Glass Transitions and Diffusion Anomalies in a Model with two Repulsive Length Scales

TL;DR

This paper uses mode-coupling theory to reveal complex glass transition behaviors and diffusion anomalies in a model with two repulsive length scales, showing novel disconnected glass-glass transitions.

Contribution

It introduces a new scenario of disconnected glass-glass transitions in a purely repulsive square-shoulder potential, expanding understanding of glassy dynamics.

Findings

Discovery of a disconnected glass-glass transition line at small shoulder widths.

Observation of diffusion anomalies similar to water.

Identification of two endpoint singularities with logarithmic decay dynamics.

Abstract

Building on mode-coupling-theory calculations, we report a novel scenario for multiple glass transitions in a purely repulsive spherical potential: the square-shoulder. The liquid-glass transition lines exhibit both melting by cooling and melting by compression as well as associated diffusion anomalies, similar to the ones observed in water. Differently from all previously investigated models, here for small shoulder widths a glass-glass line is found that is disconnected from the liquid phase. Upon increasing the shoulder width such a glass-glass line merges with the liquid-glass transition lines, featuring two distinct endpoint singularities that give rise to logarithmic decays in the dynamics. These findings can be explained analytically by the interplay of different repulsive length scales.