Low-frequency acoustic measurements on the metallic glass Zr46.8 Ti8.2 Cu7.5 Ni10 Be27.5

The properties of amorphous solids at low temperatures are well known to be dominated by atomic two-level tunneling systems (TS). While the standard tunneling model successfully describes thermodynamic properties of insulating glasses it fails to predict the elastic properties of metallic glasses. To investigate the role of conduction electrons on the density of states and the dynamics of TS vibrating reed experiments are performed. In superconducting glasses the interaction can be switched on and off by means of a magnetic field which suppresses superconductivity and therefore enables electrons to interact with TS. Here we present measurements of the internal friction and the sound velocity of the splat cooled superconducting metallic glass $\text{Zr}_{46.8}\text{Ti}_{8.2}\text{Cu}_{7.5}\text{Ni}_{10}\text{Be}_{27.5}$ measured at frequencies between 600 Hz and 14 kHz and temperatures from 10 mK to room temperature. Within these experiments we used an improved sample geometry to reduce clamping losses and to excite different modes at various frequencies.