On the overcoming of the depairing current density in the hot spot of superconducting single-photon detector

In this paper the stability of the state with vortices in a “hot spot” – the region with the suppressed order parameter in a thin superconducting film – is investigated. We perform out analysis within linear London theory, with order parameter inside the hot spot much smaller than the order parameter outside. To understand the stability of the state the energy barrier for vortex unbinding is calculated and the supermomentum at which the barrier falls to zero is found. The result demonstrates the stabilization of vortices due to repulsion from the boundaries of the hot spot, and shows that the critical supermomentum inside the hot spot exceeds the critical supermomentum in the uniform situation.