Resistive switching dynamics in current-biased YBa₂Cu₃O_7-x microbridges excited by nanosecond electrical pulses

We report our studies on the time-resolved dynamics of the superconducting-to-resistive transition in dc-biased epitaxial YBa₂Cu₃O_7-x (YBCO) microbridges, excited by nanosecond-long current pulses. Our experimental structures consisted of 200-nm-thick epitaxial YBCO films deposited on MgO substrates. They were patterned into a single 25 μm by 50 μm microbridge, embedded in the middle of a coplanar transmission line. The resistive switching was induced by the collaborative effect of both the Cooper-pair bias current and the quasiparticle pulse excitation, which together always exceeded the bridge critical current, forming the supercritical perturbation. The experimental dynamics was analyzed using Geier-Schön (GS) theory, which we modified to include the dc bias. We observed that the resistive state was established after a certain delay time t_d, which, in full agreement with the GS model, depended in a nonlinear way on both the excitation pulse magnitude and the bridge dc bias. For our nanosecond perturbations, the resistive switching dynamics was the bolometric process, limited by the phonon escape time τ_es.