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29 March 2024
 
  » arxiv » cond-mat/9609091

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Optical absorption of strongly correlated half-filled Mott-Hubbard chains
F. Gebhard ; K. Bott ; M. Scheidler ; P. Thomas ; S. W. Koch ;
Date 10 Sep 1996
Journal Phil. Mag. B 75, pp. 47-65 (1997)
Subject cond-mat chem-ph
AffiliationILL Grenoble, France), K. Bott, M. Scheidler, P. Thomas, and S. W. Koch (Philipps University Marburg, Germany
AbstractIn this last of three articles on the optical absorption of electrons in a half-filled Peierls-distorted chain we address the dimerized extended Hubbard model in the limit of a large on-site interaction $U$. When the Hubbard interaction is large both compared to the band width $W$ and the nearest neighbor interaction $V$ the charge dynamics is properly described by the Harris-Lange model. This model can be exactly mapped onto a model of free spinless Fermions in parallel (Hubbard-)bands of width $W$ which are eventually Peierls-split. To determine the coherent absorption features at low temperatures we design and employ the ``no-recoil approximation’’ in which we assume that the momentum transfer to the spin degrees of freedom can only be $Delta q_S=0$ or $Delta q_S=pi/a$ during an optical excitation. We present explicit analytical results for the optical absorption in the presence of a lattice dimerization $delta$ and a nearest-neighbor interaction $V$ for the Néel and dimer state. We find that the coherent part of the optical absorption for $V=0$ is given by a single peak at $omega=U$ and broad but weak absorption bands for $Wdeltaleq |omega-U| leq W$. The central peak at $omega=U$ only vanishes for $delta=0$ in the Néel state. For an appreciable nearest neighbor interaction $V>W/2$ almost all spectral weight is transferred to the $Delta q_C=0$-exciton and the $Delta q_C=pi/a$-exciton whose relative spectral weights very sensitively depend on both the lattice and the spin dimerization of the ground state.
Source arXiv, cond-mat/9609091
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