Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 67: Ab-initio approaches to excitations in condensed matter III

O 67.3: Talk

Friday, March 27, 2009, 11:45–12:00, SCH 251

All-electron GW calculations for SrTiO₃, BaTiO₃ and PbTiO₃ — Christoph Friedrich¹, •Andreas Gierlich¹, Arno Schindlmayr², and Stefan Blügel¹ — ¹Institut für Festkörperforschung and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany — ²Department Physik, Universität Paderborn, 33095 Paderborn, Germany

The GW approximation for the electronic self-energy, which combines bare exchange with the dynamical screening of the many-electron system within the random-phase approximation, yields quasiparticle band structures in very good agreement with experiment. While most implementations today employ the pseudopotential approximation, our recently developed realization (http://www.flapw.de/spex) is based on the all-electron full-potential linearized augmented-plane-wave (FLAPW) method, where core and valence electrons are treated on the same footing. Within this method a large variety of materials can be treated, including d- and f-electron systems, oxides and magnetic systems. In this work we present results for the perovskite transition-metal oxides SrTiO₃, BaTiO₃ and PbTiO₃, which are widely used in technical applications. Their band gaps are difficult to measure experimentally and have been under debate for a long time. Most ab initio studies so far were based on density-functional theory and showed a strong underestimation of the band gap. Here we present all-electron GW calculations that overcome this problem and yield band gaps very close to the best experimental estimates.