Ground State Phase Transition in S = 1 Distorted Kagomé Heisenberg Antiferromagnets

The ground state phase transition in the distorted S = 1 kagomé Heisenberg antiferromagnet (KHAF) is studied by means of the perturbational calculation and numerical exact diagonalization method. For strong √ 3× √ 3 lattice distortion, the hexgonal singlet solid (HSS) ground state of the uniform KHAF is destroyed and a new singlet state, the large HSS (LHSS) state, which is globally different from the HSS state is realized. The quantum phase transition between these two singlet states is analogous to the Haldane-dimer transition in the S = 1 antiferromagnetic Heisenberg chain. The presence of this transition is fully consistent with the HSS picture of the ground state of the uniform S = 1 KHAF and supports the validity of this picture.