Quantum to classical transition in the ground state of a spin-$S$ quantum antiferromagnet

TL;DR

This paper investigates how quantum antiferromagnetic ground states transition to classical magnetic order as the spin magnitude increases, using bond-operator and triplon analysis on a frustrated square lattice model.

Contribution

It introduces a scaling relation for the quantum phase transition critical couplings and incorporates quintet dimer-states to accurately describe classical order emergence for large spins.

Findings

Critical couplings scale as 1/S(S+1).

Including quintet states is essential for large S.

Classical order appears in both Heisenberg and anisotropic models.

Abstract

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.