The statistics of the ordering of chiral ribbons on a honeycomb lattice

TL;DR

This paper introduces a vertex model for chiral ribbons on a honeycomb lattice, demonstrating its equivalence to an Ising spin model on a Kagome lattice and analyzing its thermodynamic properties.

Contribution

It establishes an analytical and computational connection between a novel chiral ribbon vertex model and the well-studied Ising model on a Kagome lattice, providing insights into their ordering behavior.

Findings

Model is equivalent to an Ising spin model on Kagome lattice

Transition temperature related to energy difference as Tc=2.14J

Thermodynamic energy corrected by a factor of 1/3 for double counting

Abstract

A novel model, devised to describe spontaneous chirality synchronization in complex liquids and liquid crystals, is proposed and studied. Segments of ribbon-like molecular columns with left- or right-handed 180degree twist lie on the bonds of a honeycomb lattice so that three ribbons meet in a vertex of the hexagonal honeycomb. The energy of each vertex is a minimum if the three ribbons have the same chirality, -E, and is +E otherwise, and the ground state is homochiral, i.e. all ribbons have the same hand. The energy levels for two vertices linked by a single ribbon are either -2E, 0 and +2 E in this vertex model. Monte Carlo simulations demonstrate that this model is identical to an Ising spin model on a Kagome lattice, for which the site energy structure is quite different. The equivalence of the ordering of the vertex and Ising spin models is also shown analytically. The energy difference between the disordered and ground states, 4J in the spin model, is related to the transition temperature for the Kagome lattice using the exact result, Tc=2.14J. The ordering energy difference for a single site is 50% higher for the vertex model. The thermodynamic energy for the vertex model is corrected by a factor of 1/3 due to double counting and this makes the specific heat of the vertex model also equal to that of the spin model as expected. Other similar models where there is an unusual relation between the site and thermodynamic energies are discussed briefly.