A six-state clock-like phase transition in a coupled XY model

This study adopts the Monte Carlo simulation method to investigate a coupled XY model on triangular lattices in two dimensions. The simulation reveals a unique six-state clock-like phase transition in addition to an original XY phase transition. Analyzing the spin histograms exposes that the strong on-site coupling tends to lock the difference between the phase variables of the two XY order parameters and generates an additional phase transition. The phase transition in the model includes both continuous and discrete symmetries in some coupling parameter domain.