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Cluster approach study of intersite electron correlations in pyrochlore and checkerboard lattices

V. Yushankhai·P. Fulde·P. Thalmeier
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Abstract

To treat effects of electron correlations in geometrically frustrated pyrochlore and checkerboard lattices, an extended single-orbital Hubbard model with nearest neighbor hopping $\sim t$ and Coulomb repulsion $\sim V$ is applied. Infinite on-site repulsion, $U\to\infty$, is assumed, thus double occupancies of sites are forbidden completely in the present study. A variational Gutzwiller type approach is extended to examine correlations due to short-range $V-$interaction and a cluster approximation is developed to evaluate a variational ground state energy of the system. Obtained analytically in a special case of quarter band filling appropriate to LiV$_2$O$_4$, the resulting simple expression describes the ground state energy in the regime of intermediate and strong coupling $V$. Like in the Brinkman-Rice theory based on the standard Gutzwiller approach to the Hubbard model, the mean value of the kinetic energy is shown to be reduced strongly as the coupling $V$ approaches a critical value $V_{c}$. This finding may contribute to explaining the observed heavy fermion behavior in LiV$_2$O$_4$.

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V. Yushankhai, P. Fulde, P. Thalmeier. 2005-04-03. Cluster approach study of intersite electron correlations in pyrochlore and checkerboard lattices. https://doi.org/10.1103/physrevb.71.245108

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