56 research outputs found
Competition between reduced delocalization and charge transfer effects for a two-band Hubbard model
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-filling. Two effects determine the degree of correlation
at the surface: first, there will charge transfer between the surface and the
bulk, and, secondly, 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 quasi particle weight at
the surface is approximately equal to the bulk quasi particle weight. Only when
the charge transfer approaches zero at large interaction strengths does the
quasi particle weight at the surface become lower than that in the bulk.Comment: Accepted to Phys. Rev.
Surface effects in doping a Mott insulator
The physics of doping a Mott insulator is investigated in the presence of a
solid-vacuum interface. Using the embedding approach for dynamical mean field
theory we show that the change in surface spectral evolution in a doped Mott
insulator is driven by a combination of charge transfer effects and enhanced
correlation effects. Approaching a Mott insulating phase from the metallic
side, we show that a dead layer forms at the surface of the solid, where
quasiparticle amplitudes are exponentially suppressed. Surface correlation and
charge transfer effects can be strongly impacted by changes of the hopping
integrals at the surface.Comment: accepted in Phys. Rev.
Metallic surface of a bipolaronic insulator
We investigate the possibility that the surface of a strongly coupled
electron-phonon system behaves differently from the bulk when the relevant
parameters are inhomogeneous due to the presence of the interface. We consider
parameter variations which make the surface either more metallic or more
insulating than the bulk. While it appears impossible to stabilize a truly
insulating surface when the bulk is metallic, the opposite situation can be
realized. A metallic surface can indeed be decoupled from a bipolaronic
insulator realized in the bulk.Comment: Accepted to PR
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