Critical line of honeycomb-lattice anisotropic Ising antiferromagnets in a field

TL;DR

This study investigates the critical behavior of honeycomb-lattice Ising antiferromagnets in a magnetic field using numerical methods, revealing a finite-length critical line at constant field and challenging previous reentrant transition predictions.

Contribution

It provides a detailed numerical analysis of the phase diagram and critical properties of anisotropic honeycomb-lattice Ising antiferromagnets in a field, clarifying their phase transition behavior.

Findings

Critical line has a finite length at constant field.

No evidence of reentrant phase transitions.

Critical properties consistent with conformal invariance.

Abstract

We use numerical transfer-matrix methods, together with finite-size scaling and conformal invariance concepts, to discuss critical properties of two-dimensional honeycomb-lattice Ising spin-1/2 magnets, with couplings which are antiferromagnetic along at least one lattice axis, in a uniform external field. We focus mainly on the shape of the phase diagram in field-temperature parameter space; in order to do so, both the order and universality class of the underlying phase transition are examined. Our results indicate that, in one particular case studied, the critical line has a horizontal section (i.e. at constant field) of finite length, starting at the zero-temperature end of the phase boundary. Other than that, we find no evidence of unusual behavior, at variance with the reentrant features predicted in earlier studies.