Searching for the Gardner transition in glassy glycerol

TL;DR

This study investigates the presence of a Gardner transition in glassy glycerol by measuring nonlinear susceptibility, finding no divergence and suggesting the transition is suppressed in standard molecular glasses due to weak spin-glass interactions.

Contribution

The paper provides experimental evidence that the Gardner transition is absent in glassy glycerol, challenging mean field predictions and offering a physical explanation based on localized excitations and weak interactions.

Findings

$ ext{chi}_3^{(3)}$ decreases with cooling, not diverging.

Spin-glass interactions are much weaker than local fields.

Gardner phase likely suppressed in molecular glasses.

Abstract

We search for a Gardner transition in glassy glycerol, a standard molecular glass, measuring the third harmonics cubic susceptibility $\chi_3^{(3)}$ from slightly below the usual glass transition temperature down to $10K$. According to the mean field picture, if local motion within the glass were becoming highly correlated due to the emergence of a Gardner phase then $\chi_3^{(3)}$, which is analogous to the dynamical spin-glass susceptibility, should increase and diverge at the Gardner transition temperature $T_G$. We find instead that upon cooling $| \chi_3^{(3)} |$ decreases by several orders of magnitude and becomes roughly constant in the regime $100K-10K$. We rationalize our findings by assuming that the low temperature physics is described by localized excitations weakly interacting via a spin-glass dipolar pairwise interaction in a random magnetic field. Our quantitative estimations show that the spin-glass interaction is twenty to fifty times smaller than the local random field contribution, thus rationalizing the absence of the spin-glass Gardner phase. This hints at the fact that a Gardner phase may be suppressed in standard molecular glasses, but it also suggests ways to favor its existence in other amorphous solids and by changing the preparation protocol.