Universal power law in the orientational relaxation in thermotropic liquid crystals

TL;DR

This paper uncovers a universal power law decay in the orientational relaxation of thermotropic liquid crystals near the isotropic-nematic transition, linked to thermodynamic fluctuations of the order parameter.

Contribution

It demonstrates the emergence of power law relaxation regimes across different liquid crystal models, connecting them to thermodynamic fluctuations rather than dynamical origins.

Findings

Power law decay observed in various liquid crystal models.

Two relaxation regimes separated by a plateau near phase transition.

Power law linked to growth in orientational correlation length.

Abstract

We observe a surprisingly general power law decay at short to intermediate times in orientational relaxation in a variety of model systems (both calamitic and discotic, and also discrete) for thermotropic liquid crystals. As all these systems transit across the isotropic-nematic phase boundary, two power law relaxation regimes, separated by a plateau, emerge giving rise to a step-like feature (well-known in glassy liquids) in the single-particle second-rank orientational time correlation function. In contrast to its probable dynamical origin in supercooled liquids, we show that the power law here can originate from the thermodynamic fluctuations of the orientational order parameter, driven by the rapid growth in the second-rank orientational correlation length.