Disorder Driven Destruction of a Phase Transition in the Vortex System of a Superconductor

We investigate the effects of point disorder on the magnetically induced vortex system of a layered superconductor. The clean system is known to have a first order phase transition which is clearly identified by a sharp peak in the specific heat. The peak is lost abruptly as the strength of the disorder is increased. Hence, for strong disorder there is no phase transition (in the vortex degrees of freedom) as a function of temperature but merely a crossover which is still detectable in the I-V characteristic.