386 research outputs found
Enhancement of the thermal expansion of organic charge transfer salts by strong electronic correlations
Organic charge transfer salts exhibit thermal expansion anomalies similar to
those found in other strongly correlated electron systems. The thermal
expansion can be anisotropic and have a non-monotonic temperature dependence.
We show how these anomalies can arise from electronic effects and be
significantly enhanced, particularly at temperatures below 100 K, by strong
electronic correlations. For the relevant Hubbard model the thermal expansion
is related to the dependence of the entropy on the parameters (, , and
) in the Hamiltonian or the temperature dependence of bond orders and double
occupancy. The latter are calculated on finite lattices with the Finite
Temperature Lanczos Method. Although many features seen in experimental data,
in both the metallic and Mott insulating phase, are described qualitatively,
the calculated magnitude of the thermal expansion is smaller than that observed
experimentally.Comment: 9 pages, 6 figure
Luttinger sum rule for finite systems of correlated electrons
The validity of the Luttinger sum rule is considered for finite systems of
interacting electrons, where the Fermi volume is determined by location of
zeroes of Green's function. It is shown that the sum rule in the paramagnetic
state is evidently violated within the planar t-J model at low doping while for
the related Hubbard model, even in the presence of next-nearest-neighbor
hopping, no clearcut exception is found.Comment: 4 pages, 1 figur
Breakdown of the Luttinger sum rule within the Mott-Hubbard insulator
The validity of the Luttinger sum rule is investigated within the prototype
tight-binding model of interacting fermions in one dimension, i.e., the t-V
model including the next-nearest neighbor hopping t' in order to break the
particle-hole symmetry. Scaling analysis of finite-system results at
half-filling reveals evident breakdown of the sum rule in the regime of large
gap at V >> t, while the sum rule appears to recover together with vanishing of
the Mott-Hubbard gap.Comment: 4 pages, 5 figure
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