Competing Valence Bond Crystals in the Kagome Quantum Dimer Model
Abstract
The singlet dynamics which plays a major role in the physics of the spin-1/2 Quantum Heisenberg Antiferromagnet (QHAF) on the Kagome lattice can be approximately described by projecting onto the nearest-neighbor valence bond (NNVB) singlet subspace. We re-visit here the effective Quantum Dimer Model which originates from the latter NNVB-projected Heisenberg model via a non-perturbative Rokhsar-Kivelson-like scheme. By using Lanczos exact diagonalisation on a 108-site cluster supplemented by a careful symmetry analysis, it is shown that a previously-found 36-site Valence Bond Crystal (VBC) in fact competes with a new type of 12-site "{\it resonating-columnar}" VBC. The exceptionally large degeneracy of the GS multiplets (144 on our 108-site cluster) might reflect the proximity of the Z_2 dimer liquid. Interestingly, these two VBC "emerge" in {\it different topological sectors}. Implications for the interpretation of numerical results on the QHAF are outlined.
Cite
@article{arxiv.1109.5616,
title = {Competing Valence Bond Crystals in the Kagome Quantum Dimer Model},
author = {Didier Poilblanc and Grégoire Misguich},
journal= {arXiv preprint arXiv:1109.5616},
year = {2011}
}
Comments
8 pages, 5 figures, 4 tables; Figure 2 and Table II updated