Electron-phonon decoupling and superconducting grains

Well below Tc the electronic heat capacity of a superconductor gets dramatically small. If it were possible to use this small heat capacity for calorimetry one would have a system of very great sensitivity. The difficulty is that in a real superconductor there is also the phonon contribution to the specific heat, which will become dominant once the electronic part gets small. However, at low temperature the coupling between electrons and phonons gets progressively weaker. The isolation of the electron and phonon systems from each other may lead to a large jump in the electron temperature. Some ideas on possibly heating only the electrons in certain processes and then observing the correspondingly great jump in the electron temperature Te are examined. A test using superconducting grains is reported. (R.P.) 4 refs.; 3 figs.; 3 tabs