1H NMR and static susceptibility measurements have been performed in an organic Mott insulator with nearly isotropic triangular lattice, κ-(BEDT-TTF)2Cu2(CN)3, which is a model system of frustrated quantum spins. The static susceptibility is described by the spin S = 1/2 antiferromagnetic triangular-lattice Heisenberg model with the exchange constant J∼ 250 K. Regardless of the large magnetic interactions, the 1H NMR spectra show no indication of long-range magnetic ordering down to 32 mK, which is four-orders of magnitude smaller than J. These results suggest that a quantum spin liquid state is realized in the close proximity of the superconducting state appearing under pressure.
@article{arxiv.cond-mat/0307483,
title = {Spin Liquid State in an Organic Mott Insulator with Triangular Lattice},
author = {Y. Shimizu and K. Miyagawa and K. Kanoda and M. Maesato and G. Saito},
journal= {arXiv preprint arXiv:cond-mat/0307483},
year = {2009}
}