Lattice dynamics and electron-phonon coupling in the beta-(BEDT-TTF)(2)I-3 organic superconductor

Article

关键词: BEDT-TTF SALTS;    NONELECTROCHEMICAL SYNTHESIS;    PHYSICAL-PROPERTIES;    RAMAN-SCATTERING;    FORCE-FIELD;    AB-INITIO;    T-C;    SPECTRA;    PHASE;    BIS(ETHYLENEDITHIO)TETRATHIAFULVALENE;   

DOI  :  10.1103/PhysRevB.62.14476

来源: SCIE

【 摘 要 】

The crystal structure and lattice phonons of the (BEDT-TTF)(2)I-3 superconducting beta phase (where BEDT-TTF is bis-ethylen-dithio-tetrathiafulvalene) are computed and analyzed by the quasiharmonic lattice dynamics (QHLD) method. The empirical atom-atom potential is that successfully employed for neutral BEDT-TTF and for nonsuperconducting alpha-(BEDT-TTF)(2)I-3. The rigid molecule approximation has to be relaxed by allowing mixing between lattice and low-frequency intramolecular vibrations. Such a mixing is found to be essential to account for the specific heat measurements, and also yields good agreement with the observed Raman and infrared frequencies. The crystal structure and its temperature and pressure dependence are also properly reproduced, though the effect of the mixing is less important in this case. From the eigenvectors of the low-frequency phonons we calculate the electron-phonon coupling constants due to the modulation of charge transfer (hopping) integrals. The charge transfer integrals are evaluated by the extended Huckel method applied to all nearest-neighbor BEDT-TTF pairs in the ab crystal plane. From the averaged electron-phonon coupling constants and the QHLD phonon density of states we derive the Eliashberg coupling function alpha (2)(omega )F(w), which compares well with that experimentally obtained from point contact spectroscopy. The corresponding dimensionless coupling constant lambda is found to be similar to0.4.

【 授权许可】

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