Low frequency elastic properties of glasses at low temperatures-implications on the tunneling model

Abstract

We have measured the low frequency elastic properties of dielectric, normal conducting and superconducting metallic glasses at audio-frequencies (f≃1 kHz) and temperatures down to 10 mK. Our results are discussed in the framework of the tunneling model of glasses. The major assumption of the tunneling model regarding the tunneling states with long relaxation time has been verified, but discrepancies to high frequency measurements have been found. In addition, our experiments on superconducting metallic glasses seem to indicate that the present treatment of the electron-tunneling state interaction is not sufficient.