Francesco Sottile (LSI – Polytechnique Palaiseau)

Excitons and exciton dispersion in electronic excitations

2D map of the exciton in the first 4 Brillouin zones of hexagonal BN.

One of the simplest, yet most striking, outcomes of electron correlation is the exciton. The creation of electron-hole pair(s), under external perturbation, is an intrinsic collective excitation of the system and, from the theoretical point of view, is defined in terms of 'beyond single-particle'. In this contribution I will illustrate the importance of exciton dispersion, how it is necessary to go beyond the dipole approximation and how this can be used in a variety of experiments: Electron Energy Loss, Inelastic Xray scattering, etc.

In a second part, I will analyse the new frontiers that the exciton dispersion open, both in terms of general analysis tool and in terms of new spectroscopic features (in RIXS, in Photoemission, etc.).

 

Laboratoire des Solides Irradiés
Ecole polytechnique
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