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  • IR  (1)
  • Superconductors  (1)
  • charge defect  (1)
  • 1
    ISSN: 1572-9605
    Schlagwort(e): Superconductors ; optical properties ; High-T c
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract There is anisotropy in theab-plane optical properties of the high-temperature superconductors, both in the normal state and in the superconducting state. In both states, two components appear in the optical conductivity: a free carrier part and a “midinfrared” component. BelowT c , the free carriers form the superconducting condensate. In YBa2Cu3O7−δ, the anisotropy of the penetration depth shows that the chains contribute strongly to this superfluid. In Bi2Sr2CaCu2O8, where chains are absent, there is stillab plane anisotropy. BelowT c a finite absorption parallelb remains at frequencies as small as 20 meV. This anisotropy could be due to anisotropy either of the superconducting gap or the midinfrared component.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2395-2404 
    ISSN: 0887-6266
    Schlagwort(e): polyphenylenes ; luminescence ; broken conjugation ; discrete emitter center ; charge defect ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Optical absorption and photo-luminescence measurements were performed on a series of semiconducting polymers, based upon phenylene linkages, that have discrete emitter units. In these polymers, broken conjugation has been achieved in two ways: by introducing metalinkages between various numbers of para-connected aromatic groups or by severe steric distortion of a fully conjugated main chain. In either case, electronic states are localized on relatively small units, resulting in a large (π, π*) band gap. The band gap decreases with increasing emitter unit conjugation, as expected. Blue light emission was observed from these materials, with the peak emission wavelength red shifted (by greater than 1 eV on average) from the peak absorption. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 6 (1996), S. 353-357 
    ISSN: 1057-9257
    Schlagwort(e): IR ; TEA(TCNQ)2 ; phase transition ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Polarised infrared and optical spectra were measured at temperatures between 5 and 300 K to study the 210 K structural phase transition in the organic charge transfer salt TEA(TCNQ)2. At high temperatures, characteristic spectral features of semiconducting 1:2 TCNQ salts are observed. At low temperatures, several changes are found. First, the electronic charge transfer sharpens and has enhanced oscillator strength in the low-temperature phase. Second, the vibrational lines split into clear doublets, whose appearance is associated with a sharp decrease in the phonon damping at low temperatures.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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