The time dependent specific heat of dielectric glasses

Measurements on the time dependence of the specific heat exist now both at short and long timescales. Below 0.3 K the short time (}10 μs) specific heat of all the materials studied is smaller than the long time specific heat, but larger than the Debye value. Above 0.2 K most of the specific heat is coupled to the phonons already at 10 μs. However, measurements at very long timescales reveal that the specific heat has a component with a logarithmic time dependence, as proposed by the tunneling model, although only part of the total specific heat can be ascribed to it.