Determine the universality class of the Néel transition

Determine whether the finite-temperature transition into the Néel-ordered phase of the classical antiferromagnetic Ising model on the Shastry–Sutherland lattice remains in the two-dimensional Ising universality class for all \(0<\alpha<1\), and identify any tricritical point if the universality class changes.

Background

At $\alpha=0$, the model reduces to the square-lattice antiferromagnetic Ising model, whose transition belongs to the Ising universality class. The transition temperature is expected to decrease as $\alpha$ increases and to reach zero at $\alpha=1$.

The paper notes that the behavior of the transition line for intermediate coupling ratios has not been investigated. Results at $\alpha=0.5$ are consistent with Ising criticality, while analogy with a related square-lattice model suggests that a tricritical point might occur at some $\alpha^*\in(0.5,1)$.