Effect of the Haldane gap on quasi-one-dimensional systems

Abstract

A quasi-one-dimensional S=1 Heisenberg antiferromagnet with a single-ion anisotropy ${\mathit{Dtsum}}_{\mathit{j}}$(${\mathit{S}}_{\mathit{j}}^{\mathit{z}}$ ${)}^2$ is investigated. By treatment of interchain interactions with coupling constant J as a mean field, this system has been revealed to have a disordered ground state due to an effect of the Haldane gap, if J is small enough. By use of this approximation and application of the finite-size-scaling technique to a chain, the ground-state phase diagram in the JD plane is presented. This analysis leads to the prediction that Ni(${\mathrm{C}}_2$ ${\mathrm{H}}_8$ ${\mathrm{N}}_2$ ${)}_2$ ${\mathrm{NO}}_2$(${\mathrm{ClO}}_4$) has no Néel order even at T=0. In addition it is found that the phase transition with respect to D (<0) for a chain belongs to the two-dimensional Ising-model universality class, which agrees with Haldane’s conjecture.