Is there a spin component in the charge density fluctuations of cuprates?

Recent experimental and theoretical studies have associated the charge density fluctuations (CDF) discovered by RIXS in HTS cuprates to the strange metal phase. These short-ranged modulations survive down to extremely low doping, where magnetism rules the phase diagram. This evidence might suggest a possible role spin excitations have in the formation of these modulations. To this aim, we will investigate with RIXS YBCO at different doping levels with full polarization control of the incident and scattered beams at the CDF wavevector. The goal is to check in the CDF peak the presence, if any, of a spin-flip component due to magnetic excitations. We will therefore figure out if CDF are only made of charge, as commonly believed, or if they are characterized by a mixed spin-charge character. Ultimately, we can identify which is the driving force behind the unconventional phenomenology of the strange metal, a needed prerequisite to properly model this mysterious phase of the matter.