Resistive states created in superconducting NbTiN filaments by an electrical current pulse

We have observed as a function of the time the appearance of the voltage caused by a larger-than-critical (I > Ic) step-pulse of current in narrow NbTiN strips at 4.2 K. Different current intensities produced either phase-slip centres characterized by a voltage saturating with the time, or ever expanding hot spots. These dissipative structures occur after a measurable delay time, whose dependence upon the ratio I/Ic can be analysed through a Ginzburg-Landau theory to yield a unique adjustable time constant.