Title: Quenching current by flux-flow instability in iron-chalcogenides thin films,
Abstract: The stability against quench is one of the main issue to be pursued in a
superconducting material which should be able to perform at very high levels of
current densities. Here we focus on the connection between the critical current
$I_c$ and the quenching current $I^*$ associated to the so-called flux-flow
instability phenomenon, which sets in as an abrupt transition from the flux
flow state to the normal state. To this purpose, we analyze several
current-voltage characteristics of three types of iron-based thin films,
acquired at different temperature and applied magnetic field values. For these
samples, we discuss the impact of a possible coexistence of intrinsic
electronic mechanisms and extrinsic thermal effects on the quenching current
dependence upon the applied magnetic field. The differences between the
quenching current and the critical current are reported also in the case of
predominant intrinsic mechanisms. Carrying out a comparison with
high-temperature cuprate superconductors, we suggest which material can be the
best trade-off between maximum operating temperature, higher upper critical
field and stability under high current bias.