Bond disorder induced criticality of the three-color Ashkin-Teller model

TL;DR

This study investigates how disorder affects the phase transition in the three-color Ashkin-Teller model, revealing a new universality class with critical exponents that vary with disorder and coupling strength.

Contribution

The paper provides detailed Monte Carlo analysis showing that disorder induces a new universality class in the disordered three-color Ashkin-Teller model, with variable critical exponents.

Findings

Disorder rounds the first-order transition into a critical point.

Critical exponents vary with disorder and coupling strength.

The model does not belong to the 2D Ising universality class.

Abstract

An intriguing result of statistical mechanics is that a first-order phase transition can be rounded by disorder coupled to energy-like variables. In fact, even more intriguing is that the rounding may manifest itself as a critical point, quantum or classical. In general, it is not known, however, what universality classes, if any, such criticalities belong to. In order to shed light on this question we examine in detail the disordered three-color Ashkin-Teller model by Monte Carlo methods. Extensive analyses indicate that the critical exponents define a new universality class. We show that the rounding of the first-order transition of the pure model due to the impurities is manifested as criticality. However, the magnetization critical exponent, (\beta), and the correlation length critical exponent, (\nu), are found to vary with disorder and the four-spin coupling strength, and we conclusively rule out that the model belongs to the universality class of the two-dimensional Ising model.