Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 22: Theoretical methods

O 22.9: Talk

Monday, March 14, 2011, 19:15–19:30, WIL C107

Exchange an Correlation effects in photoemission spectroscopy: from semiconductors to transition metal oxides — •Matteo Guzzo¹, Matteo Gatti², Francesco Sottile¹, Pina Romaniello¹, Fausto Sirotti³, John Rehr⁴, and Lucia Reining¹ — ¹LSI - ETSF, Ecole Polytechnique, Palaiseau, France — ²ETSF, Universidad del Pais Vasco, San Sebastian, Spain — ³Synchrotron Soleil, Gif-sur-Yvette, France — ⁴University of Washington, Seattle WA, USA

As a prototype of strongly-correlated systems, NiO has been extensively studied, however the origin of its gap is still under debate. Many-Body Perturbation Theory (MBPT) (with the one-particle Green’s function, aka the propagator of a particle, as key quantity) describes appropriately ab-initio photoemission gaps and spectra. GW approximation from MBPT includes dynamical correlation effects beyond H-F. The standard GW approach is not reliable on NiO since the Kohn-Sham band structure is too poor a starting point. COHSEX — a static approximation of GW — allows one to achieve full self-consistency, and to obtain a better starting point for the GW step. The COHSEX+GW result gives about 5 eV energy-gap, in good agreement with experiment and with other approaches beyond G₀W₀. An attempt to apply vertex corrections from TDDFT has shown no improvement in the spectrum. Here we focus on the effects of vertex corrections on quasiparticle energies and satellites and compare the cases of Si and NiO. The Cumulant Expansion approach is discussed as a possible alternative approach.