Correlations between Soft Modes and Dynamics in Colloidal Supercooled Liquids and Glasses

The properties of matter can, in principle, be derived solely from atomic interactions and the structures of the material. In condensed materials, the fundamental role of the structure is to confine the motion of atoms, providing the spatial constraints for interacting many-body systems. In the case of crystals, regular lattices greatly reduce the complexity of theoretical calculations. For amorphous materials including liquids or glasses, however, the structural dependence of material properties is much less clear. No strutural origins have been identified for the drastic slow down of dynamics during the glass transition or the dynamical heterogeneity in supercooled liquids. In this letter, we move beyond purely geometric parameters, and focus on the confining ability of disordered structures measured by soft modes, and probe its spatial and temporal correlations to local dynamics in jammed and unjammed colloidal glasses and liquids. Strong correlations between local dynamics and soft modes are observed in jammed glasses: the local dynamics are determined by a small fraction of soft modes below and near the Boson peak, and the soft modes can be largely accounted for by measuring short time dynamics.The emergence of the correlation between soft modes and local dynamics in liquids coincides with the separation of $\alpha$ and $\beta$ relaxation time scales in supercooled liquids. This correlation begins to decay when system structure evolves beyond the Lindemann criterion, which may be universally applied in the solid-liquid transitions in both crystalline and amorphous systems.