Evidence for growing structural correlation length in colloidal supercooled liquids

Using video microscopy, we measure the long-time diffusion coefficients of colloidal particles at different concentrations. The measured diffusion coefficients start to deviate from theoretical predictions based on random collision models upon entering the supercooled regime. The theoretical diffusion relation is recovered by assigning an effective mass proportional to the size of structurally correlated clusters to the diffusing particles, providing an indirect method to probe the growth of static correlation length scales approaching the glass transition. This method is tested and validated in the crystallization of mono-disperse colloids in quasi -two-dimensional experiments. The correlation length obtained for a binary colloidal liquid increases by a power law toward a critical packing fraction of similar to 0.79. The system relaxation time exhibits a power-law dependence on the correlation length in agreement with dynamical facilitation theories.

Automated summary

By using video microscopy, the long-time diffusion coefficients of colloidal particles at different concentrations were measured. It was found that the measured values deviate from theoretical predictions in the supercooled regime. However, the theoretical diffusion relation can be recovered by assigning an effective mass proportional to the size of structurally correlated clusters to the diffusing particles, which provides an indirect method to probe the growth of static correlation length scales approaching the glass transition. This method was validated in quasi-two-dimensional experiments of crystallization of mono-disperse colloids.