Influence of the spin quantum number $s$ on the zero-temperature phase transition in the square lattice $J$-$J^{\prime }$ model

Abstract

We investigate the phase diagram of the Heisenberg antiferromagnet on the square lattice with two different nearest-neighbor bonds $J$ and $J^{\prime }$ ($J$-$J^{\prime }$ model) at zero temperature. The model exhibits a quantum phase transition at a critical value $J_c^{\prime }>J$ between a semi-classically ordered Néel and a magnetically disordered quantum paramagnetic phase of valence-bond type, which is driven by local singlet formation on $J^{\prime }$ bonds. We study the influence of spin quantum number $s$ on this phase transition by means of a variational mean-field approach, the coupled cluster method, and the Lanczos exact-diagonalization technique. We present evidence that the critical value $J_c^{\prime }$ increases with growing $s$ according to $J_c^{\prime }\propto s(s+1)$.

13 pages, 6 figures

References in corpus (1)

• Absence of magnetic order for the spin-half Heisenberg antiferromagnet on the star lattice