Capacitance and compressibility of heterostructures with strong electronic correlations
Résumé
Strong electronic correlations related to a repulsive local interaction suppress the electronic compressibility in a single-band model, and the capacitance of a corresponding metallic film is directly related to its electronic compressibility. Both statements may be altered significantly when two extensions to the system are implemented which we investigate here (i) we introduce an attractive nearest-neighbor interaction V as antagonist to the repulsive onsite repulsion U, and (ii) we consider nanostructured multilayers (heterostructures) assembled from two-dimensional layers of these systems. We determine the respective total compressibility kappa and capacitance C of the heterostructures within a strong coupling evaluation, which builds on a Kotliar-Ruckenstein slave-boson technique. Whereas the capacitance C(n) for electronic densities n close to half-filling is suppressed, illustrated by a correlation induced dip in C(n), it may be appreciably enhanced close to a van Hove singularity. Moreover, we show that the capacitance may be a nonmonotonic function of U close to half-filling for both attractive and repulsive V. The compressibility. can differ from C substantially, as kappa is very sensitive to internal electrostatic energies which in turn depend on the specific setup of the heterostructure. In particular, we show that a capacitor with a polar dielectric has a smaller electronic compressibility and is more stable against phase separation than a standard nonpolar capacitor with the same capacitance.