RESUMEN
We have measured hard x-ray photoemission spectra of pure vanadium sesquioxide (V(2)O(3)) across its metal-insulator transition. We show that, in the metallic phase, a clear correlation exists between the shakedown satellites observed in the vanadium 2p and 3p core-level spectra and the coherent peak measured at the Fermi level. Comparing experimental results and dynamical mean-field theory calculations, we estimate the Hubbard energy U in V(2)O(3) (4.20+/-0.05 eV). From our bulk-sensitive photoemission spectra we infer the existence of a critical probing depth for investigating electronic properties in strongly correlated solids.
RESUMEN
The origin of the correlation between surface reactivity and quantum-size effects, observed in recent experiments on the oxidation of ultrathin magnesium films, is addressed by means of ab initio calculations and model predictions. We show that the decay length in vacuum of the electronic local density of states at the Fermi energy exhibits systematic oscillations with film thickness, with local maxima induced when a quantum-well state at crosses the Fermi energy. The predicted changes in the decay length are expected to have a major impact on the electron transfer rate by tunneling, which has been proposed to control the initial sticking of in the oxidation process.
RESUMEN
We present the results of resonant x-ray scattering experiments on KCuF3. Structurally forbidden reflections, corresponding to magnetic and 3d-orbital long-range order, have been observed. Integrated intensities have been measured as a function of incident energy, polarization, azimuthal angle, and temperature. The results give evidence for a strong coupling between orbital and spin degrees of freedom. The interplay between magnetic and orbital order parameters is revealed by the temperature dependence of the intensity of orbital Bragg peaks.