  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 ``reentrance'' of a single intrinsic Josephson junction with
high bias current.

Superconductivity