Raman-active intramolecular CH{sub 2} and C=C vibrations and microwave surface impedance studies of the organic superconductor {kappa}-[bis(ethylenedithio)tetrathiafulvalene]{sub 2}Cu(N(CN){sub 2})Br
- Centre de Recherche en Physique du Solide, Departement de Physique, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)
We report a systematic Raman study of intramolecular vibrations for single crystals of the organic superconductor {kappa}-(BEDT-TTF){sub 2}Cu(N(CN){sub 2})Br in both the normal and superconducting states. The study has focused on the C=C stretching vibrations and the CH{sub 2} scissoring modes. From the frequency of the C=C-ring-stretching Raman mode {nu}{sub 3}({ital A}{sub {ital g}}) we estimate the average charge transfer {rho}=0.4 on the BEDT-TTF donor at 295 K while a metal-insulator transition region around 190 K is confirmed by a frequency discontinuity of the C=C ring vibrations. Frequency of CH{sub 2} vibrational modes show a discontinuity at {ital T}{sub {ital c}} that indicates a selective change in the interaction between the ethylene groups of the donor molecule BEDT-TTF and the anion (CU(N(CN){sub 2})Br){sup {minus}} while the frequency of the C=C-ring-stretching mode is blue shifted just above {ital T}{sub {ital c}}, suggesting a possible renormalization of the electron-molecular interaction. Also, in order to complement our Raman experiments and to appreciate both the crystal quality and the nature of the superconducting state in our studied samples, we present measurements, as a function of temperature, of the microwave surface impedance.
- OSTI ID:
- 55988
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 51, Issue 22; Other Information: PBD: 1 Jun 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Infrared conductivity and electron--molecular-vibration coupling in the organic superconductor di(bis(ethylenedithio)tetrathiafulvalene) bis(isothiocyanato)cuprate(I), kappa-(BEDT-TTF)/sub 2/ (Cu(NCS)/sub 2/): Protonated and deuterated salts
Superconductivity of {kappa}-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br: Isotope effect revisited[bis(ethylenedithio)tetrathiafulvalene]