Applicability of hybrid planar films of biaxial nematics for in-plane switching:A detailed Monte Carlo study

TL;DR

This study uses Monte Carlo simulations to analyze the director structures in hybrid planar films of biaxial nematics, revealing stable in-plane ordering in one type and frustrated, noisy structures in another, with implications for switching applications.

Contribution

It provides a detailed Monte Carlo analysis of biaxial nematic films with different substrate couplings, highlighting conditions for stable in-plane director structures.

Findings

Type-A film exhibits stable, noise-free in-plane director order.

Type-B film shows frustrated, noisy director configurations.

Stable in-plane ordering could be useful for switching devices.

Abstract

Equilibrium director structures in two thin hybrid planar films of biaxial nematics are investigated through Markov chain Monte Carlo simulations based on a lattice Hamiltonian model within the London dispersion approximation. While the substrates of the two films induce similar anchoring influences on the long axes of the liquid crystal molecules (viz. planar orientation at one end and perpendicular, or homeotropic, orientations at the other), they differ in their coupling with the minor axes of the molecules. In Type-A film the substrates do not interact with the minor axes at all (which is experimentally relatively more amenable), while in Type-B, the orientations of the molecular axes at the surface layer are influenced as well by their biaxial coupling with the surface. Both films exhibit expected bending of the director associated with ordering of the molecular long axes due to surface anchoring. Simulation results indicate that the Type-A film hosts stable and noise free director structures in the biaxial nematic phase of the LC medium, resulting from dominant ordering of one of the minor axes in the plane of the substrates. High degree of this stable order thus developed could be of practical interest for in-plane switching applications with an external field. Type-B film, on the other hand, experiences competing interactions among the minor axes, due to incompatible anchoring influences at the bounding substrates, apparently leading to frustration, and hence to noisy equilibrium director structures.