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Title: 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

Abstract

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 bandmore » 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.« less

Authors:
; ; ;
Publication Date:
Research Org.:
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 Identifier:
6035759
Resource Type:
Journal Article
Journal Name:
Phys. Rev. B: Condens. Matter; (United States)
Additional Journal Information:
Journal Volume: 39:16
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Sugano, T, Hayashi, H, Kinoshita, M, and Nishikida, K. 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. United States: N. p., 1989. Web. doi:10.1103/PhysRevB.39.11387.
Sugano, T, Hayashi, H, Kinoshita, M, & Nishikida, K. 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. United States. doi:10.1103/PhysRevB.39.11387.
Sugano, T, Hayashi, H, Kinoshita, M, and Nishikida, K. Thu . "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". United States. doi:10.1103/PhysRevB.39.11387.
@article{osti_6035759,
title = {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},
author = {Sugano, T and Hayashi, H and Kinoshita, M and Nishikida, K},
abstractNote = {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.},
doi = {10.1103/PhysRevB.39.11387},
journal = {Phys. Rev. B: Condens. Matter; (United States)},
number = ,
volume = 39:16,
place = {United States},
year = {1989},
month = {6}
}