We study a frustrated spin-S staggered-dimer Heisenberg model on square lattice by using the bond-operator representation for quantum spins, and investigate the emergence of classical magnetic order from the quantum mechanical (staggered-dimer singlet) ground state for increasing S. Using triplon analysis, we find the critical couplings for this quantum phase transition to scale as 1/S(S+1). We extend the triplon analysis to include the effect of quintet dimer-states, which proves to be essential for establishing the classical order (N\'eel or collinear in the present study) for large S, both in the purely Heisenberg case and also in the model with single-ion anisotropy.
@article{arxiv.1610.03826,
title = {Quantum to classical transition in the ground state of a spin-$S$ quantum antiferromagnet},
author = {Bimla Danu and Brijesh Kumar},
journal= {arXiv preprint arXiv:1610.03826},
year = {2017}
}