Low-energy excitations of the kagomé antiferromagnet and the spin-gap issue

• Published in: Europhysics letters Vol. 88; no. 2; p. 27009
• Main Authors: Sindzingre, P, Lhuillier, C
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.10.2009; EDP Sciences
• Subjects: 75.10.Jm; 75.40.Mg; 75.50.Ee
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/88/27009

In this paper we report the latest results of exact diagonalizations of $SU(2)$ invariant models on various lattices (square, triangular, hexagonal, checkerboard and kagomé lattices) and revisit critically in this light some of our previous analysis. We focus on the low-lying levels in each S sector. The differences in behavior between gapless systems and gapped ones are exhibited. The plausibility of a gapless spin liquid in the Heisenberg model on the kagomé lattice is discussed. A rough estimate of the spin susceptibility in such an hypothesis is given. The evolution of the intra-S-channel spectra under the effect of a small perturbation is consistent with the proximity of a quantum critical point. We reemphasize that the very small intra-S-channel energy scale observed in exact spectra is a very interesting information to understand the low-T dynamics of this model.