Abstract

The existence of space inhomogeneous superconductor insulator state (SISIS) found out earlier in polycrystalline samples of high-TC system Ba0.6K0.4BiO3 (TC≍30 K) is confirmed on Ba0.6K0.4BiO3 single crystal. At T* (T*<TC, T*≍17 K) the transition from the homogeneous superconducting state into the SISIS occurs. SISIS is characterized by the appearance of two gapes on the Fermi surface: semi- and superconducting, that are modulated in space in antiphase, the electric transport between superconducting regions being carried out due to Josephson tunneling. Thus the whole sample becomes a multiple Josephson system. Nonlinear I-V curves, depended on temperature and magnetic field, that are typical to a Josephson system, are observed on Ba0.6K0.4BiO3 single crystal at temperatures below T*. Besides, a step like peculiarity at the values of voltage of the order of one and two superconducting gaps shows up. These peculiarities are suppressed by magnetic field much earlier then critical current. Perhaps the last phenomenon is the consequence of “coherent” state of several successive Josephson junctions, appeared in the exfoliation state.

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