Acoustic properties of metallic glasses at low temperatures: Tunneling systems and their dephasing

The low temperature acoustic properties of bulk metallic glasses measured over a broad range of frequencies rigorously test the predictions of the standard tunneling model. The strength of these experiments and their analyses is mainly based on the interaction of the tunneling states with conduction electrons or quasiparticles in the superconducting state. A series of experiments at kHz and GHz frequencies on the same sample material essentially confirms previous measurements and their discrepancies with theoretical predictions. These discrepancies can be lifted by considering more correctly the linewidths of the dominating two-level atomic-tunneling systems. In fact, dephasing caused or mediated by interaction with conduction electrons may lead to particularly large linewidths and destroy the tunneling sytems' two-level character in the normal conducting state.

Automated summary

The study rigorously tests the predictions of the standard tunneling model by measuring the low-temperature acoustic properties of bulk metallic glasses over a broad range of frequencies. The experiments confirm the importance of the interaction between tunneling states and conduction electrons in the superconducting state. Discrepancies with theoretical predictions can be explained by considering the linewidths of the dominating two-level atomic-tunneling systems, which may be influenced by dephasing caused by interaction with conduction electrons.