Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 30: Poster Session: Disordered Quantum Systems

TT 30.3: Poster

Monday, March 12, 2018, 15:00–19:00, Poster B

Interaction of electrons with atomic tunneling systems in a Zr-basedsuperconducting metallic glass — •Arnold Seiler, Saskia M. Meißner, and Georg Weiss — Physikalisches Institut, Karlsruher Institut für Technologie

The low temperature properties of amorphous materials are known to be dominated by tunneling systems (TS) formed by atoms or groups of atoms that can tunnel between different configurations. Despite the success of the standard tunneling model in describing the properties of disordered dielectrics, its predictions for metallic glasses still appear incomplete.

In this work we investigate a Zr-based metallic glass by means of ultrasonic waves where the interaction of TS with quasiparticles or conduction electrons can be switched on and off by suppressing the superconductivity by a magnetic field. The onset of the relaxation process gives a clear indication of the energy relaxation rate of TS and allows to separate the underlying interactions and their coupling strength. Taking into account the temperature dependence of the finite linewidth and relaxation rate of TS in numerical calculations allows to reproduce the appearance of a crossing point of the sound velocity between normal and superconducting state.

Contrary to the expectation of a frequency-independent, logarithmic increase of the sound velocity with temperature, we found a frequency dependence of the temperature variation in the normal conducting state when changing the frequency of ultrasonic excitation from 1 GHz to 2 GHz.