Phase diagram of XY antiferromagnetic stacked triangular lattices

The phase transition in antiferromagnetic stacked triangular lattices with classical XY spins interacting via antiferromagnetic nearest- and next-nearest-neighbor bonds, J(1) and J(2), is studied by means of extensive histogram Monte Carlo simulations. When J(2)=0, the transition is of second order with critical exponents slightly different from those given by other authors. It is shown that in a range of J(2), the transition is of first order. The general phase diagram in the (J(2),T) space (T, temperature) is shown and discussed.