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Theoretical Spectroscopy

The Theoretical Spectroscopy Group is composed of five permanent researchers (from CNRS and Ecole polytechnique) and one system manager (CNRS), and about twelve among students and post-docs. Click here to access the official website.
The group develops fundamental theory in condensed matter and in particular on the electronic structure. More precisely, our center of interest is the electronic excitations, studied within static and time-dependent Density Functional Theory, and Many-Body Perturbation Theory. We develop ab initio theory and computer codes, and we work on both model systems for fundamental understanding and  applications of technological interest like for optoelectronics or photovoltaics.
The group is among the founders of the European Theoretical Spectroscopy Facility (ETSF), and work in tight collaborations with world-spread experimental groups expert in optical spectoscopy, electron energy loss or inelastic X-ray scattering spectroscopies.
Finally, the Theoretical Spectroscopy Group has a long-standing tradition of high-level training, both in-house and at the CECAM, where schools are regularly organised by member of the group.

 
Fig.1 Second-harmonic generation in strained silicon waveguides. Schematic representation in which the system absorbs two photons of frequency w and emits one photon of frequency 2w [1].
Contact person: Valérie Véniard Nous contacter

 
Fig.2 Excitonic wavefunction of Lithium Fluoride. The color map shows the probability to find an electron  (from low-probability in red to high-probability in blue) when a photon has been absorbed (creating a hole) in the position given by the pink ball (here on top of the Fluorine-grey atom, while Li atoms are in green). The excitonic wavefunction gives insight into the exciton character and extension [2].
Contact person: Francesco Sottile Nous contacter


Fig.3 The Many-Body problem can be cast into a set of five non-linear integro-differential equations, called Hedin's equation. This close set (five equations for five unknowns) has been written, and solved, for the specific case of one point [3].
Contact person: Lucia Reining Nous contacter

[1] Nature Materials 11, 148 (2012)
[2] Physical Review B 88, 155113 (2013)
[3] New Journal of Physics 16, 113025 (2014)