Superconducting Phase-Slip Centres at any Temperature
Résumé
The application of a supercritical current I > Ic to a narrow filament induces resistive spots of two kinds, phase-slip centres (PSC) near Tc and normal hot spots (HS) at lower temperature. The border-line between these two responses is that temperature T* that makes Ic(T*) = Ih(T*), if Ih(T) is the minimum current whose Joule dissipation maintains the film at Tc on a substrate at temperature T. It is possible, by way of thermal hysteresis, to form a PSC at T < T* by first pulsing the filament into a HS state, and then returning to a lower current I < Ih(T) < Ic(T). PSCs, characterized by their size twice the quasiparticle diffusion length and their special current-voltage relationship, were thus obtained in niobium and in epitaxial YBa2Cu3O7 strips. The primary excitation may be produced electrically or optically. Furthermore, very thin YBa2Cu3O7 strips, where Ih > Ic uniformly, support PSCs at all temperatures.