High-resolution RIXS study of the relation between acoustic plasmons and superconductivity in cuprates

Despite more than 30 years of intense research on high-Tc superconducting cuprates, a comprehensive understanding of the mechanisms that lead to their exceptionally strong superconductivity has remained elusive. Using Cu L3-edge resonant inelastic x-ray scattering (RIXS), three-dimensional collective charge excitations were revealed in electron-doped cuprates, which subsequently were also observed in hole-doped cuprates by O K-edge RIXS. Interestingly, these collective excitations correspond to the long-anticipated acoustic plasmon modes of cuprates, which were suggested to contribute to the mediation of superconducting pairing, and their evolution across Tc could reflect a possible saving of kinetic energy correlated with the superconducting transition. Here we propose an O K-edge RIXS study on the hole-doped cuprate YBa2Cu3O7 to investigate the behavior of acoustic plasmons above and below the superconducting transition and a possible relation to the elevated Tc of cuprates.