Fermion enhanced first-order phase transition and chiral Gross-Neveu tricritical point

TL;DR

This study uses quantum Monte Carlo simulations to show how massless Dirac fermions can enhance first-order phase transitions and reveal a chiral tricritical point, emphasizing the importance of finite size effects.

Contribution

It demonstrates that Dirac fermions can strengthen first-order transitions and identifies the chiral tricritical Gross-Neveu universality class at the transition point.

Findings

Yukawa coupling enlarges the first-order transition region.

Finite size effects interplay with critical fluctuations.

Scaling behavior aligns with chiral tricritical Gross-Neveu universality.

Abstract

The fluctuations of massless Dirac fermion can not only turn a first-order bosonic phase transition (in the Landau sense) to a quantum critical point, but also work reversely to enhance the first-order transition itself, depending on the implementation of finite size effects in the coupling corrections. Here, we report a case study of the latter by employing quantum Monte Carlo simulation upon a lattice model in which the bosonic part featuring the Landau-Devonshire first-order phase transition and Yukawa coupled to the Dirac fermions. We find that the parameter range for the first-order phase transition becomes larger as the Yukawa coupling increases and the microscopic mechanism of this phenomena is revealed, at a quantitative level, as the interplay between the critical fluctuations and the finite-size effects. Moreover, the scaling behavior at the separation point between the first-order and the continuous phase transitions is found to belong to the chiral tricritical Gross-Neveu universality. Our result demonstrates that the interplay of massless Dirac fermions, critical fluctuations and the finite size effects could trigger a plethora of interesting phenomena and therefore great care is called for when making generalizations.