2003/12/02 by Luca Capriotti, Tommaso Roscilde, Andrea Fubini +1
Physics and Astronomy · #cond-mat.str-el #cond-mat.stat-mech
paper · pdf · doi:10.1103/physrevlett.92.157202
published as Phys. Rev. Lett. 92, 157202 (2004) · 4 page, 4 figures
arxiv created 2003/12/02 · arxiv updated 2009/12/01
We study the thermodynamics of the spin-S two-dimensional quantum Heisenberg antiferromagnet on the square lattice with nearest (J1) and next-nearest (J2) neighbor couplings in its collinear phase (J2/J1>0.5), using the pure-quantum self-consistent harmonic approximation. Our results show the persistence of a finite-temperature Ising phase transition for every value of the spin, provided that the ratio J2/J1 is greater than a critical value corresponding to the onset of collinear long-range order at zero temperature. We also calculate the spin- and temperature-dependence of the collinear susceptibility and correlation length, and we discuss our results in light of the experiments on Li2VOSiO4 and related compounds.