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Accueil > Événements > Actualités > Séminaire

Séminaire théorie

Keith Gilmore (European Synchrotron Radiation Facility, Grenoble)
Reproducing dynamical excitations observed in resonant inelastic X-ray scattering through Bethe-Salpeter calculations
Lieu : Amphithéâtre, maison des Magistères,
le vendredi 25 mai 2018 à 11h00
Personne à contacter :

Resonant inelastic X-ray scattering (RIXS) is a relatively new technique for probing low energy excitations in materials. In addition to traditional techniques, such as angle resolved photoemission, it has become an important, high precision characterization tool of strongly correlated electron materials. To calculate RIXS, and related core and valence level spectra, we solve the Bethe-Salpeter equation (BSE) based on a self-energy corrected density functional theory electronic structure. I outline our implementation of the BSE and use SrVO3 for demonstration. Non fluorescence features in RIXS arise from a dynamic response of the system to the intermediate state perturbation. Since the Bethe-Salpeter equation is typically reduced to the static limit in practice, these dynamic excitations are generally not reproduced. To include interactions beyond the static BSE I introduce the cumulant expansion. Spectral functions derived from a GW self-energy are typically inadequate when the dressed Green’s function is built via the Dyson equation. With the same GW self-energy, a superior Green’s function and spectral function, implicitly including vertex corrections, is obtained through the cumulant expansion. I consider application of cumulant spectral functions to photoemission, photoabsorption, and X-ray scattering. Lastly, vibronic coupling has important impacts on these spectra. I show how to calculation the phonon contribution to photoemission, absorption and scattering with a vibronic cumulant.


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