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arXiv · 0706.0331

Extended Hubbard model on a C$_{20}$ molecule

Fei Lin·Erik S. Sørensen·Catherine Kallin·A. John Berlinsky
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Abstract

The electronic correlations on a C$_{20}$ molecule, as described by an extended Hubbard Hamiltonian with a nearest neighbor Coulomb interaction of strength $V$, are studied using quantum Monte Carlo and exact diagonalization methods. For electron doped C$_{20}$, it is known that pair-binding arising from a purely electronic mechanism is absent within the standard Hubbard model (V=0). Here we show that this is also the case for hole doping for $0<U/t\leq 3$ and that, for both electron and hole doping, the effect of a non-zero $V$ is to work against pair-binding. We also study the magnetic properties of the neutral molecule, and find transitions between spin singlet and triplet ground states for either fixed $U$ or $V$ values. In addition, spin, charge and pairing correlation functions on C$_{20}$ are computed. The spin-spin and charge-charge correlations are very short-range, although a weak enhancement in the pairing correlation is observed for a distance equal to the molecular diameter.

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Fei Lin, Erik S. Sørensen, Catherine Kallin, A. John Berlinsky. 2007-06-03. Extended Hubbard model on a C$_{20}$ molecule. https://doi.org/10.1088/0953-8984%2F19%2F45%2F456206

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