Classical dimers on the triangular lattice

TL;DR

This paper analyzes the classical dimer model on the triangular lattice, revealing short-range correlations and deconfinement, and explores effects of anisotropic perturbations on criticality.

Contribution

It provides an exact solution for the dimer correlations on the triangular lattice and examines how perturbations induce non-critical behavior.

Findings

Correlations are short ranged with a correlation length less than one lattice constant.

The monomer-monomer correlator decays exponentially to a constant, indicating deconfinement.

Perturbations to the lattice induce a mass term, breaking criticality.

Abstract

We study the classical hard-core dimer model on the triangular lattice. Following Kasteleyn's fundamental theorem on planar graphs, this problem is soluble by Pfaffians. This model is particularly interesting for, unlike the dimer problems on the bipartite square and hexagonal lattices, its correlations are short ranged with a correlation length of less than one lattice constant. We compute the dimer-dimer and monomer-monomer correlators, and find that the model is deconfining: the monomer-monomer correlator falls off exponentially to a constant value sin(pi/12)/sqrt(3) = .1494..., only slightly below the nearest-neighbor value of 1/6. We also consider the anisotropic triangular lattice model in which the square lattice is perturbed by diagonal bonds of one orientation and small fugacity. We show that the model becomes non-critical immediately and that this perturbation is equivalent to adding a mass term to each of two Majorana fermions that are present in the long wavelength limit of the square-lattice problem.