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Influence of the spin quantum number $s$ on the zero-temperature phase transition in the square lattice $J$-$J'$ model

R. Darradi·J. Richter·D. J. J. Farnell
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Abstract

We investigate the phase diagram of the Heisenberg antiferromagnet on the square lattice with two different nearest-neighbor bonds $J$ and $J'$ ($J$-$J'$ model) at zero temperature. The model exhibits a quantum phase transition at a critical value $J'_c > J$ 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 $J'$ 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 $J'_c$ increases with growing $s$ according to $J'_c \propto s(s+1)$.

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R. Darradi, J. Richter, D. J. J. Farnell. 2004-10-15. Influence of the spin quantum number $s$ on the zero-temperature phase transition in the square lattice $J$-$J'$ model. https://doi.org/10.1088/0953-8984%2F17%2F2%2F009

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