Reentrance of Berezinskii-Kosterlitz-Thouless-like transitions in three-state Potts antiferromagnetic thin film

TL;DR

This study uses Monte Carlo simulations to explore phase transitions in layered three-state Potts antiferromagnets, revealing reentrant Berezinskii-Kosterlitz-Thouless-like transitions and emergent symmetries.

Contribution

It uncovers a novel reentrant BKT-like transition sequence with distinct critical exponents in layered Potts antiferromagnets, expanding understanding of phase transition phenomena.

Findings

Identification of two BKT-like transitions at different temperatures.

Observation of emergent U(1) symmetry in the ordered phase.

Distinct critical exponent η=1/9 at the second transition.

Abstract

Using Monte Carlo simulations and finite-size scaling, we study three-state Potts antiferromagnet on layered square lattice with two and four layers $L_z=2$ and $4$. As temperature decreases, the system develops quasi-long-range order via a Berezinskii-Kosterlitz-Thouless transition at finite temperature $T_{c1}$. For $L_z=4$, as temperature is further lowered, a long-range order breaking the $Z_6$ symmetry develops at a second transition at $T_{c2} < T_{c1}$. The transition at $T_{c2}$ is also Berezinskii-Kosterlitz-Thouless-like, but has magnetic critical exponent $\eta=1/9$ instead of the conventional value $\eta = 1/4$. The emergent $U(1)$ symmetry is clearly demonstrated in the quasi-long-range ordered region $T_{c2} \leq T \leq T_{c1}$.