Quasi-particle spectra of perovskites: Enhanced Coulomb correlations at surfaces
Institut für Festkörperforschung, Forschungszentrum
Jülich, 52425 Jülich, Germany
Corresponding author: a email@example.com
Published online: 24 April 2003
Photoemission spectra of the perovskites CaxSrVO3, CaxLaVO3, and SrRuO3 indicate that Coulomb correlations are more pronounced at the surface than in the bulk. To investigate this effect we use the dynamical mean field theory combined with the Quantum Monte Carlo technique and evaluate the multi-orbital self-energy. These systems exhibit different degrees of band filling and range from metallic to insulating. The key input in the calculations is the layer dependent local density of states which we obtain from a tight-binding approach for semi-infinite cubic systems. As a result of the planar character of the perovskite bands near the Fermi level, the reduced coordination number of surface atoms gives rise to a significant narrowing of the surface density of those subbands which hybridize preferentially in planes normal to the surface. Although the total band width coincides with the one in the bulk, the effective band narrowing at the surface leads to stronger correlation features in the quasi-particle spectra. In particular, the weight of the quasi-particle peak near EF is reduced and the amplitude of the lower and upper Hubbard bands is enhanced, in agreement with experiments.
PACS: 71.20.Be – Transition metals and alloys / 71.27.+a – Strongly correlated electron systems; heavy fermions / 79.60.Bm – Clean metal, semiconductor, and insulator surfaces
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003