Emerging critical behavior at a first-order phase transition rounded by disorder

TL;DR

This study uses large-scale simulations to show that disorder converts a first-order phase transition in a 2D four-color Ashkin-Teller model into a continuous transition with Ising universality, confirming theoretical predictions.

Contribution

It provides numerical evidence that disorder rounds first-order transitions into continuous ones with Ising universality in the 2D Ashkin-Teller model, supporting renormalization-group predictions.

Findings

Disorder destroys the first-order transition.

Emerging transition belongs to 2D Ising universality class.

Results are consistent with theoretical predictions and previous three-color studies.

Abstract

We investigate the two-dimensional four-color Ashkin-Teller model by means of large-scale Monte-Carlo simulations. We demonstrate that the first-order phase transition of the clean system is destroyed by random disorder introduced via site dilution. The critical behavior of the emerging continuous transition belongs to the clean two-dimensional Ising universality class, apart from logarithmic corrections. These results confirm perturbative renormalization-group predictions; they also agree with recent findings for the three-color case, indicating that the critical behavior is universal.