  The response of superconducting devices to electromagnetic radiation is a
core concept implemented in diverse applications, ranging from the currently
used voltage standard to single photon detectors in astronomy. Suprisingly, a
sufficiently high power subgap radiation may stimulate superconductivity
itself. The possibility of stimulating type II superconductors, in which the
radiation may interact also with vortex cores, remains however unclear. Here we
report on superconductivity enhanced by GHz radiation in type II
superconducting Pb films in the presence of vortices. The stimulation effect is
more clearly observed in the upper critical field and less pronounced in the
critical temperature. The magnetic field dependence of the vortex related
microwave losses in a film with periodic pinning reveals a reduced dissipation
of mobile vortices in the stimulated regime due to a reduction of the core
size. Results of numerical simulations support the validy of this conclusion.
Our findings may have intriguing connections with holographic superconductors
in which the possibility of stimulation is under current debate.
