Competition between reduced delocalization and charge transfer effects for a two-band Hubbard model

Abstract

We use the embedding approach for a dynamical mean-field method to investigate the electronic properties of a semi-infinite two-band Hubbard model at half and quarter fillings. Two effects determine the degree of correlation at the surface: first, there will charge transfer between the surface and the bulk, and, second, electrons at the surface are less delocalized due to the reduced coordination number. We determine the result of these two effects and compute the quasiparticle weight. It is shown that depletion of charge from the surface to the bulk at quarter filling competes with enhanced correlation effects; the net result is that at quarter filling, the quasiparticle weight at the surface is approximately equal to the bulk quasiparticle weight. Only when the charge transfer approaches zero at large interaction strengths does the quasiparticle weight at the surface become lower than that in the bulk.