Ground State Phase Diagram of the Distorted S=1 Kagomé Heisenberg Antiferromagnets with Single-site Anisotropy

Abstract

The ground state phase transitions in the distorted S=1 kagomé Heisenberg antiferromagnet (KHAF) with single-site anisotropy D are studied by the numerical exact diagonalization method. For strong easy plane anisotropy, the hexgonal singlet solid (HSS) ground state of the uniform KHAF is destroyed and large-D state is realized. The quantum phase transition between these two states is analogous to the Haldane-large-D transition in the S=1 antiferromagnetic Heisenberg chain. The combined effect of the √3× √3 lattice distortion and single site anisotropy is also investigated. The ground state phase diagram expected from the numerical results is presented. The presence of this transition is consistent with the HSS picture of the ground state of the uniform S=1 KHAF and supports its validity.