Electronic Instability at High Flux-Flow Velocities in High-TcSuperconducting Films

At high flux-flow velocities in type-II superconductors the nonequilibrium distribution of the quasiparticles leads to an electronic instability and an abrupt switching into a state with higher electric resistivity, as predicted by Larkin and Ovchinnikov (LO). We report the first observation of this effect in a high-temperature superconductor, namely in epitaxial $c$-axis oriented films of $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$. Using the LO theory, we have extracted from our results the inelastic quasiparticle scattering rate ${\tau }_{\mathrm{in}}$, which strongly decreases with decreasing temperature below $T_c$.