Stabilization of non-self-spreading hotspots in current- and voltage-biased superconducting NbN microstrips

Electrical transport measurements were performed on superconducting NbN multicontact microstrips in order to investigate non-equilibrium dissipative states in type-II nanostructures. Current-biased and voltage-biased approaches point out the ability to stabilize a normal phase that grows discontinuously, in opposition to the usual self-spreading hotspot propagation. Results obtained by applying a dc voltage to two segments in series support this idea of a peculiar hotspot expansion. This last voltage-biasing configuration, which involves five contacts, could be used in the future to distinguish more easily between hotspot discontinuous growth and phase-slippage mechanisms.