SUPERCONDUCTING CURRENT-PHASE DEPENDENCE IN HIGH-T_c SYMMETRICAL BICRYSTAL JUNCTIONS

摘要

The dependence of the amplitudes of the harmonic and subharmonic Shapiro steps was used to study CPR of YBCO bicrystal JJ. It is shown that for a symmetric set of the transport current across the symmetric bicrystal junction the CPR is close to sinusoidal one, which differs from the theoretical predictions, based on d-type of superconducting wave function in the electrodes. The divergence from symmetry in the transport current flow across the JJ boundary causes the CPR to deviate from the sinusoidal type, with deviation increasing with increasing degree of asymmetry. This change in the CPR can be explained taking into account the formation of coupled Andreev states in a JJ of superconductors with the d-wave type superconducting order parameter. The condense superflow could be important in case of tilted bridges.