Abstract
Inspired by the recent theoretical suggestion that the random-bond antiferromagnetic Heisenberg model on the triangular and the kagome lattices might exhibit a randomness-induced quantum spin liquid (QSL) behavior when the strength of the randomness exceeds a critical value, and that this “random-singlet state” might be relevant to the QSL behaviors experimentally observed in triangular organic salts and in kagome herbertsmithite , we further investigate the nature of the static and the dynamical spin correlations of these models. We compute the static and the dynamical spin structure factors, and , by means of an exact diagonalization method. In both triangular and kagome models, the computed in the random-singlet state depends on the wave vector only weakly, robustly exhibiting gapless behaviors accompanied by the broad distribution extending to higher energy . Especially in the strongly random kagome model, hardly depends on , and exhibits an almost flat distribution for a wide range of , together with a peak. These features agree semiquantitatively with the recent neutron-scattering data on a single-crystal herbertsmithite. Furthermore, the computed magnetization curve agrees almost quantitatively with the experimental one recently measured on a single-crystal herbertsmithite. These results suggest that the QSL state observed in herbertsmithite might indeed be the randomness-induced QSL state, i.e., the random-singlet state.
9 More- Received 11 June 2015
- Revised 2 September 2015
DOI:https://doi.org/10.1103/PhysRevB.92.134407
©2015 American Physical Society