Abstract
Attractive non-local interactions jointly with repulsive local interaction in a microscopic modelling of electronic Fermi liquids generate a competition between an enhancement of the static charge susceptibility–ultimately signalling charge instability and phase separation–and its correlation induced suppression. We analyse this scenario through the investigation of the extended Hubbard model on a two-dimensional square lattice, using the spin rotation invariant slave-boson representation of Kotliar and Ruckenstein. The quasiparticle density of states, the renormalised effective mass and the Landau parameter F s0 are presented, whereby the positivity of F s0 – 1 constitutes a criterion for stability. Van Hove singularities in the density of states support possible charge instabilities. A (negative) next-nearest neighbour hopping parameter t' shifts their positions and produces a tendency towards charge instability even for low filling whereas the t'-controlled particle-hole asymmetry of the correlation driven effective mass is small. A region of instability on account of the attractive interaction V is identified, either at half filling in the absence of strong electronic correlations or, in the case of large on-site interaction U, at densities far from half filling.
Highlights
Attractive nearest neighbour interactions are commonly introduced in electronic lattice models in order to study superconductivity
We evaluated the density response from the one-loop result within slave-boson theory and extracted the dimensionless Landau parameter F0s in order to characterise the tendency towards a charge instability through a single effective interaction parameter
Our analysis builds on a 2D lattice model with two interaction scales: A positive on-site Coulomb interaction U, which may be tuned to target the regime of strong electronic correlations, and a negative nearest neighbour interaction V, which can drive a charge instability in the case of F0s ≤ −1
Summary
Attractive nearest neighbour interactions are commonly introduced in electronic lattice models in order to study (unconventional) superconductivity. Through their correlations the electrons constitute a Fermi liquid, with non-zero Landau parameters and enhanced effective mass. The Fermi liquid behaviour is expected to break down, especially if the correlations are strong close to half filling or when the attractive nearest neighbour interaction dominates.
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