Correlation and surface effects in Vanadium Oxides

TL;DR

This paper investigates surface and correlation effects in vanadium oxides using a single-band Hubbard model, revealing that surface modifications are inherent to strongly correlated electron systems and are influenced by surface coordination and hopping changes.

Contribution

It introduces a simplified dynamical mean-field approach to analyze surface spectral functions, highlighting the intrinsic nature of surface effects in strongly correlated materials.

Findings

Surface spectra show enhanced effective mass and narrowed coherent parts at the surface.

Surface correlation effects are amplified by reduced coordination and altered hopping integrals.

Surface phenomena are inherent properties of strongly correlated electron systems.

Abstract

Recent photoemission experiments have shown strong surface modifications in the spectra from vanadium oxides as (V,Cr)_2O_3 or (Sr,Ca)VO_3. The effective mass is enhanced at the surface and the coherent part of the surface spectrum is narrowed as compared to the bulk. The quasiparticle weight is more sensitive at the surface than in the bulk against bandwidth variations. We investigate these effects theoretically considering the single-band Hubbard model for a film geometry. A simplified dynamical mean-field scheme is used to calculate the main features of the interacting layer-dependent spectral function. It turns out that the experimentally confirmed effects are inherent properties of a system of strongly correlated electrons. The reduction of the weight and the variance of the coherent part of the surface spectrum can be traced back to the reduced surface coordination number. Surface correlation effects can be strongly amplified by changes of the hopping integrals at the surface.