Monte Carlo renormalization group study of the Heisenberg and the XY antiferromagnet on the stacked triangular lattice and the chiral φ4 model

With the help of the improved Monte Carlo renormalization- group scheme, we numerically investigate the renormalization group flow of the antiferromagnetic Heisenberg and XY spin model on the stacked triangular lattice (STA-model) and its effective Hamiltonian, 2N-component chiral phi(4) model which is used in the field-theoretical studies. We find that the XY-STA model with lattice size 126 x 144 x 126 exhibits clear first-order behavior. We also find that the renormalization-group flow of the STA model is well reproduced by the chiral phi(4) model, and that there are no chiral fixed points of renormalization-group flow for N = 2 and 3 cases. This result indicates that the Heisenberg-STA model also undergoes first-order transition.