Many body quantum physics in XANES of highly correlated materials, mixed valence oxides and high temperature superconductors

The x-ray absorption near edge structure (XANES), developed in these last 40 years using synchrotron radiation, is a unique tool probing electronic correlations in complex systems via quantum many body final state effects. Multi electron excitations have been observed first in the sixties in x-ray absorption spectra of atoms and later in molecules and solids. The applications of XANES many body final states to probe unique features of electronic correlation in heavy fermions, mixed valence systems, mixed valence oxides and high temperature superconductors are discussed.