Discontinuous phase transition in a dimer lattice gas

TL;DR

This paper investigates a dimer lattice gas model on a square lattice, revealing a strongly discontinuous phase transition with a significant density jump and the emergence of orientational order, supported by detailed simulations and finite-size scaling analysis.

Contribution

The study demonstrates a discontinuous phase transition in a dimer model with nearest-neighbor exclusion, linking it to the q=8 Potts model and providing detailed simulation evidence.

Findings

Density jumps by about 18% at transition

Onset of orientational order at transition

Finite-size scaling confirms discontinuous transition

Abstract

I study a dimer model on the square lattice with nearest-neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, at which the particle density jumps by about 18% of its maximum value, 1/4. The transition is accompanied by the onset of orientational order, to an arrangement corresponding to the {1/2,0,1/2} structure identified by Phares et al. [Physica B {\bf 409}, 1096 (2011)] in a dimer model with {\it finite} repulsion at {\it fixed} density. Using finite-size scaling and Binder's cumulant, the expected scaling behavior at a discontinuous transition is verified in detail. The discontinuous transition can be understood qualitatively given that the model possesses eight equivalent maximum-density configurations, so that its coarse-grained description corresponds to that of the q=8 Potts model.