Regensburg 1998 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 10: Postersitzung I: Ladungseffekte in Einelektronensystemen (1-6), Niedrigdimensionale Systeme (7-17), Transporteigenschaften und Pinning in HTSL (18-30), Symmetrie des Ordnungsparameters in HTSL (31-36), Korrelierte Elektronen: Theorie (37-79)
TT 10.30: Poster
Dienstag, 24. März 1998, 09:30–13:00, A
Nucleation of Superconductivity in Bi2Sr2CaCuO8-Whiskers — •Andreas Schley1, Hua Jin2, and J"urgen K"otzler1 — 1Institute of Applied Physics, University of Hamburg, D20355 Hamburg — 2University of Science and Technology of China, Hefei 230026, PR China
We report the first contact-free measurements of the linear electric ac-conductivity σ′+ i σ″ on Bi-2212 whiskers (typical size 3x30x2000µ m3). By means of the crossing-criterion for the phase-angle σ″/σ′[1] between 100 Hz and 1 MHz, we detect transitions to equilibrium superconductivity up to the highest field of B=0.1 T, applied here. This result is in striking contrast to previous results on Bi-2212 single crystals and thin films where superconductivity was destroyed by fields as low as 0.1 mT. Considering also the measured value of σ″/σ′ |T=Tc(B) and by extending the measurements to higher fields, we try to resolve this puzzle by discussing effects of structural disorder and critical 2D-like [2] fluctuations on the nucleation of long-range superconductivity in this strongly layered material.
[1] G. Nakielski et al., Phys. Rev. B55, 6077 (1997)
[2] J. K"otzler, M. Kaufmann, Phys. Rev. B56, 1 December (1997)