Kinetics of the current-induced phase transition in type-I superconductors

Abstract

An experimental investigation of the kinetics of the destruction of superconductivity by rectangular current pulses was made on cylindrical Sn and In wires of different purities and diameters. The study was based on the observation of the variation of the voltage along the sample during the transition. As shown by Rothen and Bestgen, only the timet ₁ between the beginning of the transition and the onset of the intermediate state can be determined with this method. The results show that if the currentI is sufficiently larger than the critical currentI _c (typicallyI⪞1.15I _c ), then both shape of the voltage pulses and the transition times agree well with the predictions of the electromagnetic theory of these authors. The transition is, in that case, controlled by the electromagnetic damping associated with the penetration into the normal material of the magnetic field due to the current. IfI is close to _c , then the transition is much slower than predicted by the theory and seems to be essentially governed by thermal effects, i.e., absorption of latent heat, generation of Joule heat, and heat exchange with the helium bath; a small influence of superheating is observed in indium samples.