Ashkin-Teller criticality and weak-first-order behavior of phase transition to four-fold degenerate state in two-dimensional frustrated Ising antiferromagnets

TL;DR

This study investigates phase transitions in two-dimensional frustrated Ising models, revealing Ashkin-Teller criticality and weak first-order behavior near four-fold degenerate states, with implications for understanding complex magnetic phase transitions.

Contribution

It demonstrates that transitions to four-fold degenerate states in 2D frustrated Ising models exhibit Ashkin-Teller criticality and similar behavior across different lattice geometries.

Findings

Identification of Ashkin-Teller-like critical behavior.

Estimation of four-state Potts-critical end points.

Observation of similar transition behavior in different models.

Abstract

We study the thermal phase transitions of the four-fold degenerate phases (the plaquette and single stripe states) in two-dimensional frustrated Ising model on the Shastry-Sutherland lattice using Monte Carlo simulations. The critical Ashkin-Teller-like behavior is identified both in the parameter regions with the plaquette and single stripe phases, respectively. The four-state Potts-critical end points differentiating the continuous transitions from the first-order ones are estimated based on finite-size scaling analyses. Furthermore, similar behavior of the transition to the four-fold single stripe phase is also observed in the anisotropic triangular Ising model. Thus, this work clearly demonstrates that the transitions to the four-fold degenerate states of two-dimensional Ising antiferromagnets exhibit similar transition behavior.