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TT: Fachverband Tiefe Temperaturen

TT 98: Poster Session: Superconductivity

TT 98.2: Poster

Donnerstag, 15. März 2018, 15:00–19:00, Poster B

Dielectric properties of thin Sn films near percolation probed with superconducting coplanar microwave resonators — •Nikolaj G Ebensperger, Martin Dressel, and Marc Scheffler — 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany

The two-dimensional limit of thin films at low temperatures opens up a plethora of interesting phenomena and physical processes. Here, knowledge of the dielectric properties at very low temperatures can be of vital help and can offer new insights into fundamental characteristics and interactions. However, the combination of thin films and very low temperatures often exceeds the limits of traditional experimental methods. We present a novel approach utilizing coplanar superconducting microwave resonators, which overcomes these difficulties, allowing precise measurements of the dielectric constant in a temperature range up to 9 K and frequency range up to 30 GHz.

Granular films are known to show peculiar behaviour of the dielectric constant approaching the percolation transition. We apply our experimental approach to thin granular Sn films with thicknesses in the range 36 - 58 nm. We determine the dielectric constant and show that it has diverging behaviour approaching the percolation threshold, similar to behaviour found in other materials with percolation transitions. At low temperatures of about 4 K we find distinct features in our data, indicating a clear superconducting transition of the individual Sn grains.