Abstract At the glass transition, a liquid transforms into an amorphous solid. Despite minimal structural rearrangements, this transition is accompanied by a dramatic dynamical slowdown. These features render the transition’s experimental determination and theoretical understanding challenging. Here we introduce a new framework that uses two-particle correlations and a model-free theoretical description to investigate the dynamics of glass-forming colloidal suspensions indirectly. Using the fluctuation-dissipation theorem, we relate equilibrium thermal fluctuations of pairs of tracer particles to the underlying response properties of the system. We measure the correlated motion of tracer particles caused by the solvent at short timescales and find three distinct signatures signalling the onset of the glass transition. The correlations in the thermal motions of tracer pairs exhibit a changing decay behaviour with their relative distance; a length scale related to this decay steeply increases; and a notable sign reversal is observed in specific correlations. Our findings establish a connection between the colloidal glass transition and the breaking of the translational symmetry in the dispersion medium, thereby revealing fundamental aspects of the glass transitions.
Laermann et al. (Fri,) studied this question.