Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.67: Poster

Montag, 27. März 2006, 14:00–17:45, P1

Low-temperature investigation on thermal properties of glasses — •Astrid Netsch¹, Sabine Wolf¹, Hsin-Yi Hao², Andreas Fleischmann¹, and Christian Enss¹ — ¹Kirchhoff-Institut für Physik, Universität Heidelberg, INF 227, 69120 Heidelberg, Germany — ²Jet Propulsion Laboratory, California Institute of Technology. Pasadena, California 91103, USA

The thermal conductivity of glasses at temperatures below 1 K is generally described by phononic thermal transport. The mean free path of the phonons is limited by scattering processes between heat-carrying phonons and tunneling systems. It seems plausible that mutually interacting tunneling systems can also contribute to thermal transport in glasses. This additional transport channel is supposed to be extremely small compared to the phononic contribution. We have performed experiments on the thermal conductivity of a glass capillary array which contains holes on a triangular lattice that serve as extra scatterers for thermal phonons. For measuring thermal conductivity of such diminutive magnitude, our contact-free technique has proven to be a suitable choice because of its extremly small parasitic heating. Our results show a thermal conductivity which varies roughly with T³ down to about 50 mK as expected for boundary scattering of phonons. Below this temperature, the thermal conductivity deviates from this dependence and follows a weaker power law. So far it is not clear whether this deviation is caused by a non-phonon contribution to the thermal transport in glasses, or if a cross-over regime occurs in which the wave length of the thermal phonons becomes comparable with the lattice constant of the array of holes.