Ordering kinetics of canted and uniform states in nematic liquid crystals

¹ School of Interdisciplinary Research, Indian Institute of Technology - Hauz Khas, New Delhi, 110016, India
² Department of Physics, Indian Institute of Technology - Hauz Khas, New Delhi, 110016, India
³ School of Physical Sciences, Jawaharlal Nehru University - New Delhi, 110067, India

Received: 14 September 2020
Accepted: 20 November 2020

Abstract

We undertake a comprehensive Monte Carlo (MC) study of the ordering kinetics in nematic liquid crystals (NLCs) in 3 dimensions by performing deep quenches from the isotropic (T > T_c) to the nematic (T < T_c) phase. The inter-molecular potential between the nematogens, represented by continuous O(3) spins with inversion symmetry, is accurately mimicked by the generalised Lebwohl Lasher (GLL) model. It incorporates second- and fourth-order Legendre interactions, and their relative interaction strength is λ. For , we observe canted morphologies with a λ-dependent angle of tilt between the neighbouring rod-like molecules. For , the molecules align to yield uniform states. The coarsening morphologies obey generalized dynamical scaling in the two regimes, but the scaling function is not robust with respect to λ. The structure factor tail in the canted regime follows the Porod law: , implying that the coarsening dynamics is due to the annihilation of interfacial defects. This is unexpected, as the GLL model is characterised by a continuous order parameter. The uniform regime on the other hand, exhibits the expected generalized Porod decay: , characteristic of scattering from string defects. Finally, the domain growth obeys the Lifshitz-Allen-Cahn law: for all values of λ. Our results for the novel canted regime are relevant for a large class of systems with orientational ordering, e.g., active matter, membranes, LC elastomers, etc. We hope that our work triggers off stimulating investigations in them.