Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2005-06-07
Phys. Rev. B 72, 214433 (2005)
Physics
Condensed Matter
Strongly Correlated Electrons
Manuscript considerably revised following referee comments. Also added a brief discussion of sum rules. 8 pages, 6 eps figures
Scientific paper
10.1103/PhysRevB.72.214433
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 La$_2$CuO$_4$, we show that an accurate fit to the magnon dispersion relation, measured by Coldea {\em et al.} [Phys. Rev. Lett. {\bf 86}, 5377 (2001)] is obtained with Hubbard model parameters $U \approx 2.34 eV$, and $t \approx 360 meV$. These parameters lead to estimates of the staggered magnetization ($m_s \approx 0.25$), spin wave velocity ($c\approx 800 meV$-\AA), and spin stiffness ($\rho_s \approx 24 meV$). In particular the staggered moment 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.
Capriotti Luca
Laeuchli Andreas
Paramekanti Arun
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