Effects of Zn substitution for Cu on Raman phonon anomalies in double-chain YBa{sub 2}Cu{sub 4}O{sub 8} superconductors
- Department of Physics, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)
- Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Sekr. 5-4, Hardenbergstrasse 36, D-10623 Berlin (Federal Republic of Germany)
- Department of Physics, The Royal Institute of Technology, S-100 44 Stockholm (Sweden)
- Department of Inorganic Chemistry, Chalmers University of Technology and University of Goeteborg, S-41296 Goeteborg (Sweden)
We report on a Raman scattering investigation of Zn-substituted ceramic YBa{sub 2}Cu{sub 4{minus}{ital x}}Zn{sub {ital x}}O{sub 8} ({ital x}=0{minus}0.05) superconductors with {ital T}{sub {ital c}} between 80 and 44 K. Anomalous temperature behavior of phonon frequencies and linewidths of the Raman-active Ba, plane-oxygen and apical-oxygen modes are observed both around 150 K, and below {ital T}{sub {ital c}} for all samples. The above-{ital T}{sub {ital c}} anomaly, which is almost independent of Zn content, can be correlated with recently reported {sup 89}Y NMR experiments that show the above {ital T}{sub {ital c}} spin-gap is only locally suppressed by the low levels of Zn doping considered here. The superconductivity related renormalizations of the Ba and plane-oxygen phonons are also largely unaffected by a decrease in {ital T}{sub {ital c}} from 80 to 44 K, indicating a complicated relation between these phonon anomalies and the superconducting gap 2{Delta}. An interpretation within the framework of the Zeyer-Zwicknagel theory (or other similar electron-phonon coupling models) would indicate that 2{Delta} is larger than about 8.7{ital kT}{sub {ital c}} in YBa{sub 2}Cu{sub 4{minus}{ital x}}Zn{sub {ital x}}O{sub 8}. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 278738
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 53, Issue 6; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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