Electron phonon interactions and superconductivity in α'-TTF[Pd(dmit)2]2
Condensed Matter Physics Group, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta-700064, India
2 Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305-8568, Japan
Corresponding author: a email@example.com
Published online: 15 November 2001
A simple model is developed to understand superconductivity in α'-TTF[Pd(dmit)2]2. We include electron-intra molecular and intermolecular phonon interactions as the mechanism of superconductivity. Intramolecular vibrations included are the eight symmetric Ag modes of the Pd(dmit)2 molecule. Intermolecular vibrations included are the longitudinal acoustic and transverse acoustic (LA and TA) modes of the Pd(dmit)2 column. All the electron-phonon coupling constants are calculated from first principles. We find that largest el-intramolecular vibration coupling is to the Ag mode with the highest frequency (1449 cm-1). The el-intermolecular coupling to the LA mode is found to be larger than the total el-intramolecular couplings. We also find el-(TA)phonon coupling to be at least an order of magnitude smaller than el-(LA)phonon coupling. Estimate of superconducting transition temperature is comparable to experimental result. We also provide a detailed discussion, employing the results of recent numerical calculations on two-chain Hubbard model and the specific material parameters, on the relative importance of el-ph and Coulomb-origin mechanisms of superconductivity in α'-TTF[Pd(dmit)2]2 and TTF[Ni(dmit)2]2.
PACS: 74.70.Kn – Organic superconductors / 74.20.-z – Theories and models of superconducting state / 63.20.Kr – Phonon-electron and phonon-phonon interactions / 74.20.Fg – BCS theory and its development
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001