Effect of local charge fluctuations on spin dynamics in La2CuO4

[摘要] We explore the effect of local charge fluctuations on the spin response of a Mott insulator by deriving an effective spin model, and studying it using Schwinger boson mean field theory. Applying this to La2CuO4, we show that an accurate fit to the magnon dispersion relation, measured by Coldea [Phys. Rev. Lett. 86, 5377 (2001)] is obtained with Hubbard model parameters U approximate to 2.34 eV, and t approximate to 360 meV. These parameters lead to estimates of the staggered magnetization (m(s)approximate to 0.25), spin wave velocity (c approximate to 800 meV A), and spin stiffness (rho(s)approximate to 24 meV). In particular the staggered magnetization as well as the effective local moment are renormalized to smaller values compared to the Heisenberg model due to local charge fluctuations in the Hubbard model. The dynamical structure factor shows considerable weight in the continuum along the zone boundary as well as secondary peaks that may be observed in high resolution neutron scattering experiments.

[发布日期] 2005-12-01

[关键词] FILLED HUBBARD-MODEL;HEISENBERG-ANTIFERROMAGNET;EXCITATIONS;EXCHANGE;MAGNON