Superconducting fluctuations and {sup 63}Cu NQR-NMR relaxation in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}: Effect of magnetic field and a test for the pairing-state symmetry
- Department of Physics ``A. Volta,`` Sezione di Pavia, Istituto Nazionale di Fisica Nucleare and Unita Instituto Nazionale di Fisica della Materia, University of Pavia, Via Bassi 6, I-27100, Pavia (Italy)
- Department of Theoretical Physics, Moscow Institute of Steel and Alloys, 117936 Moscow (Russia)
Evidence is presented of superconducting fluctuations in the {sup 63}Cu NQR-NMR relaxation rate in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, as obtained from a careful comparison of measurements carried out in the absence and in the presence of a field parallel to the {ital c} axis. It is shown that the field causes a reduction of the relaxation rate {ital W} in a range of about 10 K above {ital T}{sub {ital c}}. This effect is related to the suppression by the magnetic field of the phase-sensitive positive Maki-Thompson contribution while the negative contribution from the DOS fluctuations is almost field independent. Furthermore, it is argued how the fluctuation effects on {ital W} can be used to discuss the pairing state symmetry, at variance with the insensitivity of the transport measurements. It is pointed out that the existence of the Maki-Thompson contribution to {ital W} evidences an {ital s}-wave symmetry component for the pairing in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 385729
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 54, Issue 14; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
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