Charge segregation is very common in correlated oxides, and ranges from the extreme limit of the Mott insulators (complete charge localization) to “softer” charge-density-wave phases (partial charge re-organization). In order to probe the occurrence and evolution of such phenomena along the periodic table, we have studied the strongly-correlated 3d-oxides and the spin-orbit-coupled 5d-oxides. These investigations have been performed with a bundle of state-of-the-art spectroscopic techniques in the field of quantum materials, namely: angle-resolved photoemission (ARPES), resonant X-ray scattering (RXS), scanning tunnelling microscopy (STM) and optical spectroscopy. To support experimental data, we have used theoretical tools such as conventional density-functional theory for the 5d-oxides and developed ad-hoc approaches for the more complex 3d-materials.

The all-around study of underdoped high-Tc Bi-based cuprates has allowed us to shed new light on the universality and origin of charge-ordering instabilities in these materials and understand their interplay with superconductivity and pseudogap. In the 5d-based iridates (in particular, Na2IrO3) we have revealed and characterized a novel form of Mott-Hubbard physics. This helped demonstrate the crucial role of spin-orbit interaction in keeping correlations alive even outside the limits set by the Mott criterion.