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

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.39.11387· OSTI ID:6035759

Sugano, T; Hayashi, H; Kinoshita, M; Nishikida, K

Polarized reflectance spectra of the organic superconductors protonated and deuterated kappa-(BEDT-TTF)/sub 2/(Cu(NCS)/sub 2/) (H and D salts) (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) were measured over the range from 500 to 28 000 cm/sup /minus/1/ at room temperature with light polarizations parallel to the crystallographic /ital b/ and /ital c/ axes which lie on the two-dimensional conducting plane. Polarized reflectance spectra of the organic superconductor ..beta..-(BEDT-TTF)/sub 2/I/sub 3/ and the organic metal ..beta..''-(BEDT-TTF)/sub 2/AuBr/sub 2/ were also measured in order to discuss the influence of different molecular arrangements and hydrogen-anion contacts on the electronic and vibrational properties of these salts. Frequency-dependent conductivities were calculated by a Kramers-Kronig transformation. By comparison of the infrared conductivity spectra of the H and D salts, the vibrational transitions induced by electron--molecular-vibration (EMV) coupling were clearly distinguished from the carbon-hydrogen bending modes of the BEDT-TTF moiety. A Drude-Lorentz dielectric function was used to evaluate the optical transport parameters and an excitation frequency of the charge-transfer (CT) band superimposed on a plasma-edge-like dispersion which was observed for each compound. The EMV-coupling energies are semiquantitatively estimated to be ca. 70 meV for both the H and D salts from the frequencies of the EMV coupling transition and the CT band in terms of the dimer charge-oscillation model. By use of the coupling energy, various parameters describing the superconducting state were evaluated and discussed on the basis of the BCS theory in a weak-coupling limit. Finally, the magnitudes of hydrogen-anion interaction were estimated from the frequency shifts of the C-H bending modes of the BEDT-TTF moiety.

• Research Organization: The Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan(JP); Perkin-Elmer Japan, Kitasaiwai, Nishi-ku, Yokohama 220, Japan
• OSTI ID: 6035759
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Vol. 39:16
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BEDT-TTF
LIGHT SCATTERING
CUPRATES
ELECTRON-MOLECULE COLLISIONS
ELECTRON-PHONON COUPLING
INFRARED SPECTRA
LATTICE VIBRATIONS
MEDIUM TEMPERATURE
POLARIZATION
REFLECTION
SALTS
SUPERCONDUCTORS
COLLISIONS
COPPER COMPOUNDS
ELECTRON COLLISIONS
HETEROCYCLIC COMPOUNDS
MOLECULE COLLISIONS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
SCATTERING
SPECTRA
TRANSITION ELEMENT COMPOUNDS
656100* - Condensed Matter Physics- Superconductivity