https://doi.org/10.1140/epjb/e2003-00122-7
Quasi-particle spectra of perovskites: Enhanced Coulomb correlations at surfaces
Institut für Festkörperforschung, Forschungszentrum
Jülich, 52425 Jülich, Germany
Corresponding author: a a.liebsch@fz-juelich.de
Received:
22
January
2003
Published online:
24
April
2003
Photoemission spectra of the perovskites CaxSrVO3,
CaxLa
VO3, 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