Electrical Polarizability of Phonon Scattering States in Glasses
Tunneling states1 in glasses should be electrically polarizable. Hence one might expect that the thermal conductivity would change in an electric field. In two previous studies, no effect was seen2,3. In the first experiment, however, the dielectric polarizability of the glass was not known, and the sensitivity of the experiment was reduced because of the relatively high temperatures used, T > 2° K. In the second experiment, the experiment was performed at lower temperatures (T > 0.15°K), and the polarizability was measured. The latter, however, was found to be quite small, which again should decrease the sensitivity of the experiment. In the present experiment, we have chosen a glass of very high polarizability, and have also measured as low as 0.2° K. The experimental technique was the same as that used by Stephens3. The soda-silica glass sample had the composition 75 wt% SiO2, 12 wt% Na2O, with the remainder B2O3, K2O, and Al2O3. The relative change in thermal conductivity, defined as Δ Λ/Λ = (Λ(E,T) - Λ (O,T) ) /Λ(O,T) in an applied field as high as 53 kV/cm, is shown in Fig. 1. As in the previous studies, no systematic change was detectable. In zero field, the thermal conductivity was found to scatter within the range indicated by the two curves in Fig. 1, arising mostly due to thermal drift.
KeywordsThermal Conductivity Dipole Moment Silica Glass Electrical Polarizability Tunneling Model
Unable to display preview. Download preview PDF.