Magnetic excitation spectra of strongly correlated quasi-one dimensional systems: Heisenberg versus Hubbard-like behavior

Abstract

We study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum -- with low-energy peaks resembling spinonic excitations -- already at intermediate on-site repulsion as small as $U/t\sim 2-3$, although ratios of peak intensities at different momenta continue evolving with increasing $U/t$ converging only slowly to the Heisenberg limit. We discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of $U/t$ of quasi-one dimensional systems described by one-orbital Hubbard models from experimental information.

10 pages, 9 figures

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• Root-N Krylov-space correction-vectors for spectral functions with the density matrix renormalization group
• SU($\mathbf{N}$) Kondo-Heisenberg chain: Phase diagram, Ising criticality, and the coexistence of heavy quasiparticles and valence bond solid order
• Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi-Hubbard model