CDW investigation of La2-xSrxCoO4 by soft x-ray scattering*

Recently, charge density wave (CDW) states have been proved to be practically ubiquitous in copper based high temperature superconductors (HTSCs). Questions on their nature and relation to superconductivity (SC) are considered crucial for understanding the pairing interaction at play in these unconventional materials.
La2-xSrxCoO4 (LSCoO), isostructural to Sr-doped La2CuO4 although without a SC phase, has also revealed a spin density wave (SDW) and some evidences for a CDW order in neutron scattering studies.
We report relevant results on CDW in the series, obtained by soft x-ray scattering at Co L3 of CDW.
The accessible Co states (two oxidation and spin states) offer a peculiar view on the system, allowing to separate the electronic degrees of freedom involved. The information retrieved as a function of temperature reveals the relation between the various orderings in the system, highlighting the role of doping charges in TMO2 planes. Interesting deductions can be drawn from the comparison with HTSC compounds.