THE EFFECT OF HOTSPOT FORMATION ON QUASI-PARTICLE YIELDS IN SUPERCONDUCTING ALUMINUM FILMS

Existing models show that any hotspot created in an Al film following a particle interaction is rapidly diluted. Quasiparticles and phonons decouple at high energies so that on short time-scales quasiparticle d iffusion determines the energy transport. Few quasiparticles have ener gies near the energy gap and there is little gap suppression. We have measured the initial quasiparticle yields in very thin Al films and fi nd somewhat surprisingly that this yield is reduced. It appears that a short time-scale quasiparticle loss mechanism, probably associated wi th localised over-injection, exists as quasiparticles scatter to low e nergies within the phonon hotspot.