Dipolar order controls dielectric response of glass-forming liquids

TL;DR

This study demonstrates that dipolar order influences the dielectric response in glass-forming liquids, linking the Kirkwood correlation factor to the dielectric loss spectrum, and confirms recent theories while challenging previous models.

Contribution

It establishes a correlation between dipolar order and dielectric response in supercooled liquids, providing experimental validation for recent theoretical predictions.

Findings

High-frequency dielectric loss exponent correlates with dipolar order.

Confirmed the role of dipolar cross-correlations in dielectric spectra.

Results challenge the earlier Kivelson-Madden theory.

Abstract

The dielectric response of liquids reflects both, reorientation of single molecular dipoles and collective modes, i.e., dipolar cross-correlations. A recent theory predicts the latter to produce an additional slow peak in the dielectric loss spectrum. Following this idea we argue that in supercooled liquids the high-frequency power law exponent of the dielectric loss $\beta$ should be correlated with the degree of dipolar order, i.e., the Kirkwood correlation factor $g_K$. This notion is confirmed for 25 supercooled liquids. While our findings support recent theoretical work the results are shown to violate the earlier Kivelson-Madden theory.