抄録
The temperature Tb dependence of current density j at the boundary of hotspot has been measured for granular aluminum thin films immersed in superfluid helium, whose temperature is Tb. The thickness d dependence of j-Tb characteristics, shows that the heat transfer from hotspot to superfluid helium, is almost limited by the thermal resistance between the electrons and lattice for thin films, d=14 and 28 nm. But, for a thicker film, d=112 nm, the Kapitza resistance must be considered in addition to the above thermal resistance.
Close to the superconducting transition temperature Tc, a finite region of Tb in which j is proportional to (Tc−Tb)3⁄2, has been found. This characteristic is explained by theoretical results derived under the assumption that Joule heating depends not only on current density but also on temperature of the electrons.
