Phase transitions in the quantum easy-plane antiferromagnet on the triangular lattice

The quantum effects on the thermodynamics of the easy-plane triangular antiferromagnet, displaying classically both an Ising and a Berezinskii-Kosterlitz-Thouless phase transition, are evaluated by means of the pure-quantum self-consistent harmonic approximation, which allows one to deal with any spin value through classical Monte Carlo simulations. Data for the specific heat, the static spin correlation functions, and the in-plane correlation length are presented in a broad range of temperatures, for different values of the spin and of the exchange anisotropy. Our results for the quantum transition temperatures are in good agreement with the few available theoretical and numerical estimates.