Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 30: Poster Session: Disordered Quantum Systems
TT 30.2: Poster
Montag, 12. März 2018, 15:00–19:00, Poster B
Dielectric measurements of the dynamics of atomic tunneling systems in thin-film AlOx — •Saskia M. Meißner, Arnold Seiler, and Georg Weiss — Physikalisches Institut, Karlsruher Institut für Technologie
From the study of glasses atomic tunneling systems (TS) are well known to dominate the low temperature properties of disordered materials. They also appear in thin-film dielectrics of superconducting circuits, where AlOx is a common material for the fabrication of Josephson junctions.
We present a broadband study of the dynamics of TS contained in thin-film disordered AlOx ranging from kHz to GHz frequencies. The TS’ density of states is probed at kHz frequencies by capacitance measurements as well as in the GHz range by tracking the resonance frequencies of superconducting microstrip resonators with embedded plate capacitors. This geometry creates a homogeneous electric field which is concentrated in the dielectric AlOx reducing the influence of the native oxide on the surface of the Al structures.
The large bandwidth of excitation frequencies allows to verify the standard tunneling model but contrary to the predictions we measured an increasing density of TS with increasing temperature. Moreover, our observations reveal that the relaxation rates of TS are not only caused by their interaction with phonons and other TS as expected in dielectrics but also by quasiparticles penetrating the AlOx from the superconducting Al plates.