Slow Change of the Electron Clouds of Ions: a Common Medium for Electron Pairing in Laofep, Nb and Tlba2cacu2o7

The author proposes that the change of the electron clouds of ions can be a new electron-pairing medium in unconventional superconductors. Real-time evolution of the electron clouds of ions in LaOFeP, Nb and TlBa2CaCu2O7 was calculated by the time-dependent density functional theory (TDDFT). The natural frequencies of the change of the electron clouds were obtained. The author found, for the first time, the frequencies are close to those of the lattice vibrations. The characteristic frequencies are 280 meV, 160 meV, 208 meV and 140 meV, respectively, for different ions, showing that the change of the electron clouds of the ions can be the electron-pairing medium. Iron-based superconductors, copper-based superconductors and superconductors which do not conform to isotope effects or cannot be explained by electron-phonon interactions may all have a common electron-pairing medium: the change of the electron clouds of ions.