RIXS investigation of double-chain superconducting cuprate YBa2Cu4O8

The direct observation and characterization of both collective spin excitations, proposed to be crucial to pairing, and charge density waves (CDW), which compete with superconductivity and are ubiquitous in all cuprate families, proved to be extremely important for our knowledge of high-Tc compounds. A big component of this years-long RIXS quest aimed at understanding spin and charge ordering phenomena in cuprates has focused on YBa2Cu3O6+x as a model system, owing to its limited doping-induced disorder. Sporting a similar crystal structure but hosting a double chain layer, YBa2Cu4O8 (Y124) is the only cuprate possessing a stoichiometric composition with highly robust oxygen content, thereby offering a unique, defect-free system for investigations in the underdoped regime. However, to date the reduced dimension of single crystals complicated the alignment and measurements of Y124 in standard soft RIXS setups.