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TT: Tiefe Temperaturen

TT 6: Solids At Low Temperature: Amorphous and Tunnel Systems, Glasses, ...

TT 6.6: Vortrag

Montag, 27. März 2006, 12:00–12:15, HSZ 105

Thermal Conductivity of Glasses and the "Boson Peak" — •Walter Schirmacher — Technische Universität München, Phys. Dept. E13, D-85747 Garching

A theory for the anomalous vibrational and thermal properties of disordered solids based on the model assumption of randomly fluctuating transverse elastic constants is presented. Mean-field expressions for the vibrational density of states and the energy diffusivity are derived with field theoretical techniques. As in previous approaches of this type the boson peak (enhancement of the low-frequency density of states) is explained as a result of the frozen-in disorder and compares well with the experimental findings. The plateau in the temperature variation of the thermal conductivity and the behavior beyond the plateau is shown to arise from the enhanced scattering in the boson peak regime and to be essentially a harmonic phenomenon.