The Theory Group conducts in-house research in theoretical physics and assists scientists and users of the ESRF beamlines with theoretical questions related to the interpretation of experimental results and the conception of new experiments.The research carried out in the Theory Group concerns mostly solid state theory, with a particular emphasis on magnetism, unconventional properties of strongly correlated materials and X-ray spectroscopy. In particular, we are currently working on the following topics:

  • Theory of quantum spin systems and molecular magnets. Here our activity addresses the quantum dynamics of spin systems in the quantum regime (Patrick Bruno). This work applies directly to molecular magnets, but has implications for various apparently unrelated problems, such as ultra-cold quantum gases or superconducting mesoscopic devices.
  • Iron-based superconductors. In the intense research on these recently discovered materials, our research focuses on the exotic electronic properties of the normal state, which create the suitable conditions for high-temperature superconductivity to arise (Luca de' Medici).
  • Hund's physics in metallic states. Hund's rules, well known in atomic physics, have a surprisingly important and diversified influence on metallic states of d-electron materials, including on the Mott transition, and on the possible coexistence of conduction electrons with different correlation strength. We study and characterize that with many-body techniques such as Dynamical Mean-Field Theory and Slave-Spin Mean-Field, both on realistic ab-initio and model calculations (Luca de' Medici).
  • X-ray spectroscopy. We develop first-principles methods to model various x-ray spectra including x-ray absorption (XAS), x-ray emission (XES), and both resonant and non-resonant inelastic x-ray scattering (N/RIXS). Calculations are based in density functional theory with self-energy corrections and spectra are obtained by evaluating the Bethe-Salpeter equation for the excited electron and core-hole (Keith Gilmore).