Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 21: Solids at Low Temperature - Poster Session
TT 21.13: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
Low-temperature investigation of the thermal properties of glasses — •Astrid Netsch, Sabine Wolf, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institut für Physik, Universität Heidelberg, INF 227, 69120 Heidelberg, Germany
The thermal conductivity of glasses at low temperatures is generally believed to be due to the propagation of phonons. However, a second transport channel for heat should exist in these materials because of the existence of tunneling systems that interact with each other and allow for a diffusion of energy via resonant flip-flop processes. This contribution is expected to be much smaller than that due to phonons. In search of such a contribution we have performed measurements on two planar glass samples which contain holes of different size on a triangular lattice that serve as extra scatterers for phonons. For measuring thermal conductivity of such diminutive magnitude we used a SQUID-based contact-free technique because of its extremly small parasitic heating. Our results show that the thermal conductivity varies roughly with T3 down to about 50 mK as expected for phonons in the boundary scattering regime. Below this temperature, the thermal conductivity follows a weaker power law. Though this is expected for thermal transport via mutually interacting tunneling systems the absolute value appears to be surprisingly high compared to theoretical predictions. Therefore it remains an open question whether the observed deviation is indeed caused by a non-phononic contribution, or whether this is a consequence of the wave length of the phonons becoming larger than the lattice constant of the array of holes.