Electron-phonon interactions, pair-transfer processes, and superconductivity inTTF[Ni(dmit)2]2

A model is developed for superconductivity in ${\mathrm{TTF}\left[\mathrm{Ni}\right(\mathrm{dmit})\mathrm{}}_2{]}_2.$ We include both electron-intramolecular and -intermolecular vibration couplings. These interactions are the principal sources of superconducting pairing. The electron-intramolecular vibration coupling constants are estimated after performing a complete normal-mode analysis. The electron-intermolecular vibration coupling constants are also estimated. The unique band structure of this material [with both highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) derived bands crossing the Fermi level] leads to a pair-transfer term between the bands. Estimates for $T_c$ are in reasonable agreement with experimental results. We find that major contribution to the electron-phonon interaction, in this material, comes to the LUMO band from acoustic phonons and pair transfer processes reduce the effects of the intraband Coulomb repulsion.