Electron-phonon coupling in 1D edge-shared cuprates probed by resonant soft x-ray scattering

Resonant inelastic x-ray scattering (RIXS) is a powerful probe for studying excitations in strongly correlated systems. With continued advancements of the technique, the overall energy resolution has improved to the point of uncovering low-energy bosonic excitations near the elastic line. In this talk we present evidence for coupling to an optical oxygen phonon in the RIXS spectrum of the quasi-1D edge shared cuprate Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$ at the oxygen K-edge. This mode is identified as a compressive mode polarized perpendicular to the chain direction which modulates the Cu-O charge transfer energy which sets the size exchange interaction. By comparing to small cluster calculations we extract a sizable electron-phonon coupling strength and infer an interplay between the electronic, magnetic, and lattice degrees of freedom.