EN
The motion of the magnetic flux quanta in the
mixed state of a type-II superconductor, due to the Lorentz
force of an electric transport current, represents the key
mechanism for generating resistive losses. Whereas the
most common result is Joule heating of the superconductor,
also purely electronic non-equilibrium effects can
play a dominant role in the case of effective cooling of
the sample. The latter situation can be realized by means
of very thin superconducting films (having a large surface/
volume ratio). In this paper we discuss experiments
with Nd2−xCexCuOy (NCCO) films performed some time
ago, yielding evidence for electronic non-equilibrium effects
due to the energy dependence of the quasi-particle
density of states in the mixed state of the films. The films
were imbedded within super-fluid helium for cooling. The
recent advances in the fabrication of epitaxial ultra-thin
superconducting films promise to contribute to further
clarification of these electronic non-equilibrium effects.