Dynamics and Time Scales of Higher-Order Correlations in Supercooled Colloidal Systems

The dynamics and time scales of higher-order correlationsare studiedin supercooled colloidal systems. A combination of X-ray photon correlationspectroscopy (XPCS) and X-ray cross-correlation analysis (XCCA) showsthe typical slowing of the dynamics of a hard sphere system when approachingthe glass transition. The time scales of higher-order correlationsare probed using a novel time correlation function g ( C ), tracking the time evolution of cross-correlationfunction C. With an increasing volume fraction, theratio of relaxation times of g ( C ) to the standard individual particle relaxation time obtainedby XPCS increases from similar to 0.4 to similar to 0.9. While a value of similar to 0.5 is expected for free diffusion, the increasing valuessuggest that the local orders within the sample are becoming morelong-lived for larger volume fractions. Furthermore, the dynamicsof local order is more heterogeneous than the individual particledynamics. These results indicate that not only the presence but alsothe lifetime of locally favored structures increases close to theglass transition.

Automated summary

The dynamics and time scales of higher-order correlations in supercooled colloidal systems were studied using X-ray photon correlation spectroscopy (XPCS) and X-ray cross-correlation analysis (XCCA). The results showed the typical slowing of the dynamics of a hard sphere system when approaching the glass transition. The time scales of higher-order correlations were probed using a novel time correlation function g(C), revealing that the local orders within the sample become more long-lived for larger volume fractions.