Buckling phonons in cuprates: a very high resolution RIXS study

The role of phonons in the high Tc superconductivity of cuprates is still hotly debated. Recently, new experimental findings and theoretical arguments have pointed out that buckling phonons may play a major role in the physics of these materials due to the large electron-phonon coupling (EPC). Among other, the buckling mode is expected to vary more among cuprates, as an effect of the different static buckling of the CuO2 planes, being the Cu-O-Cu angle almost 180° in infinite layer compounds and of several degrees off in LSCO and YBCO. Here, we propose to exploit the 25 meV Bandwidth, soon available at ID32 thanks to an ongoing upgrade of the optics, to investigate by Resonant Inelastic X-ray Scattering the buckling modes of 3 cuprate families. For the first time the EPC of the buckling mode will be mapped systematically, in search for a correlation between the EPC, the buckling and the presence of apical oxygen.