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Vie de l'Institut - Institut de minéralogie, de physique des matériaux et de cosmochimie

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Ab initio methods for excitons, resonances and band excitations in time and frequency domain - Maurits Haverkort - Jeudi 4 février 2016 à 14 h

 

IMPMC - Université P. et M. Curie - 4, Place Jussieu - 75005 Paris


Salle de Conférence - Barre 22-23 - 4e étage - Salle 401


Maurits Haverkort - 
Max Planck Institute for Chemical Physics of Solids, Dresden


Abstract

The theoretical description of the dynamics and excitations of many materials can be quite challenging. It often requires a treatment beyond standard mean-field Hartree-Fock or density functional theory approximations. Where the ground-state to some degree can be approximated by a single Slater determinant this is much less the case for excited states. The "hole" that the excited electron leaves behind can interact in a non-trivial way with the excited electron and other valence electrons around. Depending on the strength of these interactions one observes band-excitations, resonances or excitons.
In this talk I will show how a newly developed post density functional theory method, merging ideas from quantum chemistry and renormalization group theory can capture the comple spectrum, of interaction range. This allows us to describe excitations including many-body effects that lead to excitonic behavior, multiplets and electronic entanglement. It furthermore allows us to study the decay of such local excitations into continuum states, leading to resonances with characteristic asymmetric Fano type lineshapes.
In the second part of the talk I will show how one can extend these methods to the time domain. This allows one to describe the propagation of excitations and their various decay channels as seen in pump probe experiments.