Raman spectroscopy of the high T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ and the semiconductor YBa/sub 2/Cu/sub 3/O/sub 6/
The recent discoveries of superconducting materials with extraordinarily high-transition temperatures immediately raise the question of whether an electron-phonon mechanism as in the Bardeen-Cooper-Schrieffer (BCS) theory is operative or if some entirely new mechanism must be invoked. The common structural features of these materials are extended Cu-O chains and sheets. Since the standard BCS theory predicts that T/sub c/ is proportional to the Debye temperature, it has been suggested that the comparatively high frequencies of Cu-O breathing modes could be responsible for these very high-transition temperatures. Motivated by the generally accepted empirical correlation between the existence of phonon anomalies, lattice instabilities, and high T/sub c/'s in other materials, the authors have begun to investigate the role of lattice phonons in high T/sub c/ superconductors. They report here the Raman spectra of the superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ phase and the semiconducting YBa/sub 2/Cu/sub 3/O/sub 6/ phase. A high-frequency mode was identified in the Raman spectrum of the high temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ which is shifted to much lower frequencies in the oxygen deficient nonsuperconducting compound YBa/sub 2/Cu/sub 3/O/sub 6/. This mode is assigned to the symmetric stretch of the terminal Cu-O bonds in the linear chain of corner-shared CuO/sub 3/ units; this assignment is consistent with the structural models derived from diffraction experiments. While these experiments do not definitively establish a causal link between the frequency shift of this mode and susperconductivity, the correlation is nevertheless intriguing.
- Research Organization:
- Univ. of Texas, Austin
- OSTI ID:
- 6043110
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:17; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
DATA
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
INFORMATION
LASER SPECTROSCOPY
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RAMAN SPECTROSCOPY
SPECTROSCOPY
SUPERCONDUCTIVITY
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
VIBRATIONAL STATES
YTTRIUM COMPOUNDS
YTTRIUM OXIDES