Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 33: Amorphe- und Tunnelsysteme, Gl
äser

TT 33.3: Vortrag

Freitag, 12. März 2004, 10:45–11:00, H19

Low-temperature investigation on thermal conductivity of glasses — •H.-Y. Hao¹, M. Neumann¹, A. Rost¹, A. Fleischamnn¹, C. Enss², and S. Hunklinger¹ — ¹Kirchhoff-Institut fuer Physik, Universitaet Heidelberg — ²Department of Physics, Brown University

The thermal conductivity of glasses at temperatures below 1 K is generally described through the resonant scattering between the heat-carrying phonons and the tunnuling systems in the glasses. At further low temperature, it is evident that the interactions between the tunneling systems themselves could be responsible for describing the anomalies observed in certain properties of glasses. It is therefore conceivable that such interactions could also contribute to the heat transport and become visible when the phonons are frozen out at very low temperatures or suppressed by some additional scattering mechanism introduced to the system. For measuring thermal conductivity of such diminutive magnitude, our recently developed contact-free technique is proved to be ideal owing to its surpassingly small parasitic heating to the system. Measurements on bulk BK7 glass and synthetic quartz glass have been successfully preformed down to 5 mK. For reducing the phonon mean-free-path, a glass capillary array is used to introduce extra scattering of the thermal phonons. For such a sample, an advanced design of the setup is developed to improve the precision of the measurements. Preliminary findings will be presented and discussed.