Suppression of the superconducting energy gap in intrinsic Josephson junctions of Bi2Sr2CaCu2O8+δ single crystals

We have observed back-bending structures at high bias current in the current–voltage curves of intrinsic Josephson junctions. These structures may be caused by nonequilibrium quasiparticle injection and/or Joule heating. The energy gap suppression varies considerably with temperature. Different levels of the suppression are observed when the same level of current passes through top electrodes of different sizes. Another effect which is seen and discussed is a super-current 're-entrance' of a single intrinsic Josephson junction with high bias current.