paper

Static and dynamical spin correlations of the S=1/2 random-bond antiferromagnetic Heisenberg model on the triangular and the kagome lattices

arXiv:1506.03576 · doi:10.1103/PhysRevB.92.134407

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 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 wavevector only weakly, robustly exhibiting gapless behaviors accompnied 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 semi-quantitatively with the recent neutron-scattering data on a single-crystal herbertsmithite, suggesting that the QSL state observed in herbersmithite might indeed be the randomness-induced QSL state, {\it i.e.\/}, the random-singlet state.

To appear in Phys. Rev. B. One figure (Fig. 9) and one reference (Refs. 82) added. Some of the text part expanded

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