A vortex crossing a thin-film superconducting strip from one edge to the other, perpendicular to the bias current, is the dominant mechanism of dissipation for films of thickness $d$ on the order of the coherence length $\xi$ and of width $w$ much narrower than the Pearl length $\Lambda \gg w\gg \xi$. At high bias currents $I^{*}<I<I_c$ the heat released by the crossing of a single vortex suffices to create a belt-like normal-state region across the strip, resulting in a detectable voltage pulse. Here $I_c$ is the critical current at which the energy barrier vanishes for a single vortex crossing. The belt forms along the vortex path and causes a transition of the entire strip into the normal state. We estimate $I^{*}$ to be roughly $I_c/3$. Furthermore, we argue that such “hot” vortex crossings are the origin of dark counts in photon detectors, which operate in the regime of metastable superconductivity at currents between $I^{*}$ and $I_c$. We estimate the rate of vortex crossings and compare it with recent experimental data for dark counts. For currents below $I^{*}$, that is, in the stable superconducting but resistive regime, we estimate the amplitude and duration of voltage pulses induced by a single vortex crossing.

• Received 10 February 2011

DOI:https://doi.org/10.1103/PhysRevB.83.144526