Correlation between optical phonon softening and superconducting in YBa2Cu3Ox within d-wave Eliashberg theory

Abstract

We provide a mathematical description, based on d -wave Eliashberg theory, of the strong correlation between the experimentally observed softening of Raman modes associated with in-plane oxygen motions and the corresponding superconducting critical temperature $T_\mathrm{c}$ , as a function of oxygen doping x , in YBa _2 Cu _3 O _x . The theoretical model provides a direct link between physical trends of soft optical A _g (in-plane) oxygen modes, the level of oxygen doping x , and the superconducting $T_\mathrm{c}$ . Different regimes observed in the trend of $T_\mathrm{c}$ vs doping can be related to corresponding regimes of optical phonon softening in the Raman spectra. These results provide further evidence related to the physical origin of high-temperature superconductivity in rare-earth cuprate oxides and to the significant role of electron–phonon coupling therein.

Keywords

• superconductors
• phonon softening
• oxygen doping
• Raman spectroscopy
• high-T superconductivity
• charge density waves