Confinement effects on magnetic excitations in cuprate superconductors

The role of spin excitations in the formation of Cooper pairs in high-temperature cuprate superconductors is still controversial. Our recent RIXS measurements at the ESRF reported anomalies in the magnon peak shape for YBCO thin films cut along the (103) crystal surface compared to c-axis oriented films. At present, it is unclear whether the shape of the magnon is actually anomalous or a different kind of excitation adds up in the same energy range. The goal of the present proposal is an extensive investigation of the magnon dispersion by means of combined energy, momentum and polarization analysis, in order to test the hypothesis that these effects are caused by the spin confinement along one in-plane direction.