Expérimental et théorique
A recent spectroscopic technique reported in March 2019 enables the direct imaging of orbitals. The measurement is based on Non-resonant Inelastic X-ray Scattering (NIXS) by observing some low-energy absorption resonance in the energy loss spectrum (incident minus final energy). The method has been successfully applied in NiO with a 3d8 electronic configuration, revealing the dz2 and dx2-y2 orbitals of the 3d holes of Ni atoms (see figure from Nature Physics 15, 559 (2019)). This new kind of imaging opens up a wide and completely new field of investigations, in particular for strongly correlated electrons materials where small changes of electronic structure generate remarkable properties (heavy fermions, superconductors, Mott insulators etc…)