Phase transitions in the frustrated antiferromagnetic XY model on the triangular lattice

Phase transitions and thermodynamics properties of the frustrated antiferromagnetic XY (FAXY) model have been investigated near the two transition temperatures. We found that the Kosterlitz-Thouless (KT) transition corresponding to the rotational U(1) symmetry breaking and the Ising-like (I) transition corresponding to the reflection Z₂ symmetry breaking occur at two-separate transition temperatures, T_kt < T_I. These temperatures lie close to each other, however in our results the separation is obvious. Our results show the order parameters as a function of temperature and we also estimate the critical exponents, β, α, γ, η and ν. The critical exponent ν indicates that the Ising-like transition is inconsistent with the Ising universality class.