Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 19: Poster Session: Disordered Quantum Systems

TT 19.2: Poster

Monday, April 1, 2019, 15:00–18:30, Poster D

Direct Probing of the Nuclear Quadrupole Impact onto Tunnelling Systems in Glasses at Low Temperatures — •Aljoscha Auer, Lukas Münch, Benedikt Frey, Andreas Schaller, Andreas Reiser, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University

The low temperature behaviour of amorphous solids are often well described with the phenomenological standard tunneling model (STM), which assumes a distribution of two level systems (TLS) inside the glass. However, several experiments like polarisation echo experiments and dielectric measurements on glasses containing large nuclear quadrupole moments have shown significant deviation from the STM. Thus over the years several extensions revolving around the coupling of Nuclear Quadrupole Moments (NQM) to local electric field gradients were proposed.

To get a better understanding of this mechanism we measured the TLS dynamics via the dielectric permittivity. Hereby we tune the frequency to the nuclear quadrupole frequency. In the second experiment we measured the low frequency dielectric permittivity using a superconducting interdigital capacitor surrounded by a single-loop coil. This coil enables us to apply a radio-frequency magnetic field at the dominant quadrupole splitting frequency to the sample, while directly measuring the dielectric response. We will present this new approach as well as current data from both experiments.