Low-temperature transient thermal anomalies in vitreous quartz

Fast-time (10–100 microseconds) heat-pulse methods have been employed to obtain simultaneously the specific heats and thermal diffusivities of vitreous quartz at low temperatures. The experiments were designed to look for a time dependence in the specific heat as predicted by the tunneling model used to describe the low-temperature thermal properties of amorphous materials. No time dependence was observed over the range 0.6 to 3.4 kelvins when the pulses were analyzed using the response predicted by standard heat-diffusion theory. However, a large, reproducible, and systematic dependence on the input energy of the heat pulse was observed in the measured properties of our samples.