Phase transitions in a triangular Blume-Capel antiferromagnet

TL;DR

This study investigates phase transitions in a frustrated triangular Blume-Capel antiferromagnet, revealing a novel Berezinskii-Kosterlitz-Thouless phase and characterizing its critical behavior through Monte Carlo simulations.

Contribution

It is the first to identify a BKT phase in the frustrated Blume-Capel model, expanding understanding of phase transitions in frustrated magnetic systems.

Findings

Discovery of a BKT phase with power-law correlations

Identification of a first-order transition for certain anisotropy values

Consistency of decay exponents with six-state clock model predictions

Abstract

We study the critical behavior of a frustrated Blume-Capel (BC) antiferromagnet on a triangular lattice by Monte Carlo simulations. For a reduced single-ion anisotropy strength $-1.47 \lesssim d < 0$ we find two phase transitions. The low-temperature phase is characterized by the antiferromagnetic long-range ordering (LRO) on two sublattices with the third one remaining in a non-magnetic state. At higher temperatures there is a critical region of the Berezinskii-Kosterlitz-Thouless (BKT) type with a power-law decaying spin-correlation function. For $-1.5 \le d \lesssim -1.47$, there is only one phase transition from the LRO to the paramagnetic region and the transition is of first order. The presence of the BKT phase in the current frustrated BC model is a new feature not observed in its non-frustrated counterparts. The values of the decay exponent $\eta$ of the BKT phase corresponding to upper and lower temperatures appear to be consistent with the theoretical predictions for the six-state clock model.