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Raman study of the coupling of crystal-field excitations to phonons in NdBa sub 2 Cu sub 3 O sub 7 minus. delta

Journal Article · · Physical Review, B: Condensed Matter; (United States)
; ; ;  [1]
  1. Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-7000 Stuttgart 80 (Germany)
A double peak observed near 300 cm{sup {minus}1} in the Raman and inelastic-neutron-scattering spectra of the high-{ital T}{sub {ital c}} superconductor NdBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} is due to a strong coupling and mixing of the {ital B}{sub 1{ital g}}-symmetry Raman phonon and crystal-field (CF) excitations of the Nd{sup 3+} 4{ital f} electrons of the same symmetry. In this paper, we describe in detail a model based on the coupling of extended phonons and localized CF excitations. Higher phonon quantum numbers have to be taken into account at room temperature. We show that this interpretation is compatible with measurements of the dependence on temperature, oxygen isotopic substitution, laser wavelength, and oxygen content. We obtain from our model the CF-phonon coupling constant as well as the frequencies of the unperturbed phonon and CF excitation. We also discuss the breaking of the polarization selection rules for the highest phonon based on the substitution of Ba by Nd ions.
OSTI ID:
6222295
Journal Information:
Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 44:18; ISSN PRBMD; ISSN 0163-1829
Country of Publication:
United States
Language:
English