Heat Release in Solids

Abstract

In this chapter we will discuss two consequences of the tunneling model that is used to understand the low-temperature properties of amorphous and disordered solids: a time-dependent specific heat and the corresponding time-dependent heat release. This “heat release” (often referred to as “energy relaxation”) is the warming-up effect observed in a sample that is cooled from a temperature T ₁ to a measuring temperature T ₀ without an external heat input. To our knowledge, it appears that the first comment in literature on heat release is given by Greywall (1978). He found a time-dependent heat leak in a calorimeter made from Plexiglas (mass m=15g) that he correctly brought in connection with the amorphous nature of this material, but he did not extend his considerations. This task has been done later by Zimmermann and Weber (1981a), who actually introduced heat-release measurements as a new method to investigate the properties of amorphous solids. Together with the first systematic measurements of the heat release in Suprasil W, Zimmermann and Weber (1981a) were the first to propose a quantitative analysis of the data. After this publication, numerous measurements of the heat release on various materials have been done. Nowadays this method can be considered as established to characterize the anomalous low-temperature properties of disordered solids due to tunneling processes.