MPI für Festkörperforschung / FKF Publikationen 2006 |
|Isotope effect on the optical phonons of YBa2Cu4O8 studied by far-infrared ellipsometry and Raman scattering|
|Authors:||Trajnerowicz, A.; Golnik, A.; Bernhard, C.; Machtoub, L.; Ulrich, C.; Tallon, J. L.; Cardona, M.|
|Date of Publication (YYYY-MM-DD):||2006|
|Title of Journal:||Physical Review B|
|Issue / Number:||10|
|Sequence Number of Article:||104513|
|Abstract / Description:||The phonon spectra of YBa2Cu4O8 polycrystalline samples with different
isotope substitution for Ba, Cu, and O have been studied using
far-infrared ellipsometry and Raman scattering. The observed isotope
shifts of Raman- and infrared-active phonons provide insight into their
relative Ba, Cu, and O normal mode content. This allows us to examine
mode eigenvectors obtained from lattice dynamical calculations using ab
initio electronic structures based on the full potential linear
muffin-tin-orbital within the local density approximation. Our Raman
results demonstrate that the 104 cm(-1) A(g) phonon is only very weakly
mixed, representing almost pure Ba vibrations. Correspondingly the 151
cm(-1) phonon represents pure Cu vibrations. The 339, 436, and 498
cm(-1) phonon modes involve mainly O vibrations. Considerable Cu-O
mixing takes place in the case of the A(g) phonons at 257 and 605
cm(-1) and for the B-3g phonon at 314 cm(-1). These results are in good
agreement with the ab initio calculations. The far-infrared experiments
reveal that the modes with energies of 115, 297, 502, and 592 cm(-1)
are mixed vibrations of O and Cu atoms. The phonon mode at 130 cm(-1)
corresponds to a Ba-Cu-O complex whereas the modes at 191 and 357
cm(-1) reflect almost pure Cu and O vibrations, respectively.
|External Publication Status:||published|
|Communicated by:||N. N.|
|Affiliations:||MPI für Festkörperforschung|
|External Affiliations:||Univ Warsaw, Inst Expt Phys, PL-00681 Warsaw, Poland.
; Max Planck Inst Festkorperforsch, D-70569 Stuttgart, Germany.
; Univ Fribourg, Dept Phys, CH-1700 Fribourg, Switzerland.
; New Zealand Inst Ind Res, Lower Hutt, New Zealand.
|Identifiers:||ISI:000240872000083 [ID No:1] |
ISSN:1098-0121 [ID No:2]
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