Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 12: Frontiers of Electronic-Structure Theory: Focus on the Interface Challenge II (joint session O/CPP/DS/TT)
TT 12.2: Talk
Monday, April 1, 2019, 15:15–15:30, H9
Momentum-Resolved Electron Energy-Loss Spectroscopy in Oxides from Many-Body Perturbation Theory — •Christian Vorwerk1,2, Caterina Cocchi1,2, and Claudia Draxl1,2 — 1Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany — 2European Theoretical Spectroscopy Facility
Electron energy-loss spectroscopy (EELS) is a powerful tool to investigate the local electronic and structural properties of crystalline materials. The accurate determination of these spectra from first principles requires a reliable description of the electron-hole interaction, screened by the surrounding many-electron system. We perform ab initio many-body perturbation theory calculations of EELS through the solution of the Bethe-Salpeter equation (BSE), including the screened non-local interaction between electron and hole. Employing an implementation in the all-electron full-potential package exciting, we show results for a wide range of energy loss, from the optical to the hard x-ray region. We study EELS at finite momentum loss q, from small q close to the dipole limit to large q well beyond the first Brillouin zone. This momentum resolution of EELS reveals dipole-forbidden excitations that are invisible in absorption spectroscopy. Our calculations also yield insight into the excitonic dispersion, i.e. the excitonic bandstructure. We discuss the effects of momentum loss in the EELS spectra of oxide materials, including CaO, CeO2, and the wide-gap transparent oxide Ga2O3, considering both the optical and x-ray energy-loss range.