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TT: Tiefe Temperaturen
TT 23: Posters Superconductivity, Solids at Low Temperature
TT 23.62: Poster
Monday, March 7, 2005, 14:00–18:00, Poster TU D
Low-temperature investigation on thermal properties of glasses — •Astrid Netsch, Hsin-Yi Hao, Sabine Wolf, Andreas Rost, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institut für Physik,Universität Heidelberg, Im Neuenheimer Feld 227, D-69120 Heidelberg
The thermal conductivity of glasses at temperatures below 1 K is generally described by phonon thermal transport. The mean free path of the phonons is limited by scattering processes between the heat-carrying phonons and the tunneling systems in the glasses. At further low temperature, it is possible that the interactions between the tunneling systems also contribute to the thermal conductivity. To investigate such an additional heat transport mechanism one has to reduce the phonon mean-free-path to cut down the phonon contribution. That means one has to make some restrictions to the geometry of the glass sample.
We present measurements of the thermal conductivity of a glass capillary array which is used to introduce extra scattering of the thermal phonons. For measuring thermal conductivity of such diminutive magnitude, our contact-free technique is proved to be ideal owing to its surpassingly small parasitic heating to the system. Our results show a thermal conductivity, which varies proportional to T3 down to about 50 mK as expected for boundary scattering. Below this temperature the heat transport deviates from this dependence, being larger than expected. This might be an indication for non-phonon thermal transport of heat in glasses.