Superconducting-gap symmetry study using a/c boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} films
- Superconductivity Research Laboratory, International Superconductivity Technology Center, 1-10-13 Shinonome, Koto-ku, Tokyo 135 (Japan)
We have investigated gap symmetry of high-T{sub c} superconductors using Josephson junctions formed along a boundary of an a-axis-oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) grain surrounded by c-axis-oriented YBCO grains (a/c boundary). There are two types of a/c boundary junctions; one is the boundary between (001) of a-axis-oriented grains and (100) of c-axis-oriented grains, and the other is the boundary between (001) of a-axis-oriented grains and (110) of c-axis-oriented grains. TEM observation shows clean, sharp, and nearly single-facet interface along the grain boundaries in both types. In the case of the (100)-(001) type a/c boundary junction, typical resistively shunted junction (RSJ)-type I-V curves, Shapiro steps under microwave irradiation, and Fraunhofer-like diffraction pattern of I{sub c} under magnetic field are observed, indicating that the boundary works as a Josephson junction. In the case of the (110)-(001)-type a/c boundary junction, typical RSJ type I-V curves and Shapiro steps under microwave irradiation are also observed. However, the diffraction pattern of I{sub c} under magnetic field has the minimum value at zero magnetic field. This property is analogous to one observed for a corner junction which is formed between Pb and YBCO. These results show that the (110) of YBCO has a phase difference of {pi} and d{sub x{sup 2}{minus}y{sup 2}} superconducting-gap symmetry is in CuO{sub 2} planes of YBCO. But, the (001) of YBCO has no phase difference of {pi} in spite of the existence of d-wave symmetry in YBCO. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 496751
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 55, Issue 17; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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