| Abstract: | We report on thec-axis superconducting energy gap parameter Δ
c
(T) of intrinsic Josephson tunnel junctions inBi
2
Sr
2
CaCu
2
O
8+δ (Bi2212) single crystals. Δ
c
(4.2K)≈10−13 meV, which is approximately a factor of two smaller than reported in the majority of tunneling experiments. Δ
c
(T) deviates strongly from the BCS temperature dependence. These observations may be explained by a multilayer model of Bi2212
which assumes that theBi−O layers are superconducting due to the proximity effects. The Josephson tunneling then takes place between adjacentBi−O layers while there is a strong proximity coupling betweenBi−O andCu−O layers.
The work is supported by Swedish Supercon-ductivity Consortium and NUTEK, and, in part, by Russian Foundation for Basic Research,
grant #95-02-04307 |
