Resonance Raman investigations of the symmetric stretching mode of I/sub 3/ /sup -/ anions in. cap alpha. and. beta. phases of di-bis(ethylenedithio)tetrathiafulvalene tri-iodide
The resonance Raman spectra of I/sub 3/ /sup -/ anions in the organic superconductor ..beta..-(BEDT-TTF)/sub 2/I/sub 3/ (BEDT-TTF represents bis(ethylenedithio)tetrathiafulvalene) were studied and discussed in comparison with the nonsuperconducting phase of ..cap alpha..-(BEDT-TTF)/sub 2/I/sub 3/. In both modifications at low temperature a splitting of the Raman mode assigned to the symmetric stretching mode of the I/sub 3/ /sup -/ anions was discovered. The splitting of this mode in the ..beta..-(BEDT-TTF)/sub 2/I/sub 3/ crystals is related to the commensurate superstructure developed below 125 K in contradiction to the ..cap alpha.. phase where the splitting is related to a crystal-field effect. It is shown that an electronic excitation of the ..beta..-phase crystals by laser light can induce a structural transformation at least in a thin layer of the surface. This transformation is observed by a disappearance of the splitting of the symmetric stretching mode. The structural change can be related to a transformation from the commensurate superstructure with a superconducting transition temperature T/sub c/ = 1.3 K into a more ordered and symmetric structure which becomes superconducting at T/sub c/ = 8.1 K.
- Research Organization:
- Max-Planck-Institut fuer Medizinische Forschung, Abteilung fuer Molekulare Physik, Jahnstrasse 29, 6900 Heidelberg, West Germany
- OSTI ID:
- 5573133
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 36:13
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BEDT-TTF
LATTICE VIBRATIONS
RAMAN SPECTRA
SUPERCONDUCTIVITY
ANIONS
CRYSTAL FIELD
CRYSTAL-PHASE TRANSFORMATIONS
MOLECULAR STRUCTURE
ORDER-DISORDER TRANSFORMATIONS
RESONANCE
RESPONSE FUNCTIONS
CHARGED PARTICLES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FUNCTIONS
HETEROCYCLIC COMPOUNDS
IONS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SPECTRA
360603* - Materials- Properties
656100 - Condensed Matter Physics- Superconductivity