Temperature dependence of the dielectric function of nonmetallic YBa2Cu3Ox in the interband range from transmission and reflection measurements on thin films

✍ Scribed by R. Boyn; D. Wruck; M. Merbach; J.-P. Müller

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 616 KB
• Volume: 228
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)90172-4

✦ Synopsis

The interband dielectric function of nonmetallic YBa2Cu3Ox at energies below 4.5 eV, for E_I_ c polarisation, is obtained from transmission and reflection measurements on epitaxial thin films between 1.8 and 473 K. A significant temperature dependence is found, in particular, for the 1.75 eV and 4.1 eV features, and this is discussed in terms of electron-phonon interaction. For the 1.75 eV excitation, two models are used to analyse this dependence, one based on largely localised transitions (configurationcoordinate model) and one (recently introduced by Falck et al. [Phys. Rev. Lett. 69 (1992) 1109] ) starting from delocalised excitations. Both models lead to a reasonable description of the data. For the 4.1 eV excitation, a configuration-coordinate analysis is presented. It is found that, for both excitations, one is dealing with rather strong coupling to phonons, probably from the whole phonon spectrum.