Nonlocal dielectric relaxation in glycerol

Since its introduction, liquid viscosity and relaxation time $\tau$ have been considered intrinsic properties of a system that is essentially local in nature and therefore independent of system size. Dielectric relaxation experiments are performed in glycerol, and it is discovered that this is the case at high temperature only. At low temperature, $\tau$ increases with system size and becomes nonlocal. We discuss the origin of this effect in the theory based on liquid elasticity length, the length over which local relaxation events in a liquid interact via induced elastic waves. We find good agreement between experiment and theory.

Figure 1

Schematic experimental setup (inset) and typical dielectric loss spectra of glycerol measured in the larger (circles) and smaller (squares) capacitors at $T=233$ K.

Figure 2

(a) $\tau$ in large (upper symbols) and small (lower symbols) capacitors. The horizontal long-dashed line corresponds to $\tau$, above which the size effect is predicted to exist. (b) $\log \left({\tau }_1\right)-\log \left({\tau }_2\right)$, where ${\tau }_1$ and ${\tau }_2$ are relaxation times in large and small capacitors, respectively.