Monte Carlo Study of Chiral Criticality —XY and Heisenberg Stacked-Triangular Antiferromagnets

The results of extensive Monte Carlo simulations are reported on XY and Heisenberg antiferromagnets on a d{=}3-dimensional stacked-triangular lattice, which are expected to belong to the recently identified n{=}2 and 3 chiral universality classes, respectively. The lattices studied consist of L³ spins with 18≤L≤60. The study is an extension of earlier Monte Carlo simulations for the same system with smaller lattices. A continuous transition characterized by the novel critical exponents is found with α{=}0.34± 0.06, β{=}0.253± 0.01, γ{=}1.13± 0.05 and ν{=}0.54± 0.02 for the XY (n{=}2) case, and with α{=}0.24± 0.08, β{=}0.30± 0.02, γ{=}1.17± 0.07 and ν{=}0.59± 0.02 for the Heisenberg (n{=}3) case. The specific-heat amplitude ratio is estimated to be A⁺/A^-{=}0.36± 0.2 and A⁺/A^-{=}0.54± 0.2 in the n{=}2 and n{=}3 cases, respectively. The nature of the chiral ordering is also studied, and various chirality exponents are determined. The results are discussed in conjunction with the recent renormalization-group calculations and experiments.