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Low field63Cu NMR study of indirect nuclear spin-spin coupling in YBa2Cu3O6.9. A new approach to probe strong correlation effects in high-T c superconductors |
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| Authors: | T. Imai C. P. Slichter A. P. Paulikas B. Veal |
| Affiliation: | 1. Science and Technology Center for Superconductivity, University of Illinois at Urbana-Champaign, 1110 West Green Street, 61801, Urbana, IL, USA 2. Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, 61801, Urbana, IL, USA 3. Department of Chemistry, University of Illinois at Urbana-Champaign, 1110 West Green Street, 61801, Urbana, IL, USA 4. Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, 61801, Urbana, IL, USA 5. Materials Science Division Argonne National Laboratory, Argonne, USA |
| Abstract: | The authors carried out a low field (6.3 kOe) NMR measurement of the Gaussian component of63Cu nuclear spin-spin relaxation rate 1/T 2G at the planar Cu site in a high-T c superconductor YBa2Cu3O6.9 (T c=92 K). They demonstrate that the results provide quantitative information concerning the static spin susceptibility χ′(q) at non-zero wave vector q. The detailed analysis of the data assuming a model susceptibility peaked at the corner of first Brillouin zone q=Q (Q=(π/a, θ/a),a: lattice constant) shows that χ′(q) satisfies a Curie-Weiss law around q=Q. Stoner enhancement over the calculated Lindhard function at q=Q is estimated to be of the order of ～10–20. They also demonstrate that combined analysis of 1/T 1 and 1/T 2G allows one to judge whether anomalous shift of the low frequency spectral weight of χ″(Q,ω) to higher frequencies (i.e.pseudo gap) exists or not. Application of the method to YBa2Cu3O6.9 revealed no appreciable pseudo gap in the material. |
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