SKM 2021 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 22: Poster Session: Disordered and Granular Superconductors: Fundamentals and Applications in Quantum Technology

TT 22.8: Poster

Thursday, September 30, 2021, 13:30–16:00, P

Modified properties of disordered superconducting films with amorphous and granular structure — •Mariia Sidorova^1,2, Alexej Semenov¹, Stephan Steinhauer³, Samuel Gyger³, Val Zwiller³, Xiaofu Zhang⁴, Andreas Schilling⁴, and Heinz-Wilhelm Hübers^1,2 — ¹DLR, Institute of Optical Sensor Systems, Berlin, Germany — ²Humboldt-Universität zu Berlin, Berlin, Germany — ³KTH Royal Institute of Technology, Stockholm, Swede — ⁴University of Zürich, Zürich, Switzerland

Thin disordered superconducting films are intensively exploited in various superconducting devices, for instance, superconducting single-photon detectors (SSPDs) and hot-electron bolometers (HEBs). The dimensionality of such films usually duffers with respect to various physical phenomena, for instance, it is two-dimensional (2d) to superconductivity and weak localization, three-dimensional (3d) to normal conduction, and approach a 2d-3d crossover with respect to phonons. Properties of low-dimensional systems differ from bulk materials and their either theoretical or empirical description remains very limited.

We have studied several superconducting films with thicknesses below 10 nm and different morphology: amorphous WSi and polycrystalline granular NbN and NbTiN. Employing magnetoconductance and calorimetric measurements, we derived an electron-phonon scattering rate and determined sound velocities and phonon heat capacities. Our results indicate a systematic reduction of the sound velocity in all films as compared to the corresponding bulk crystalline material, and a significant impact of the film morphology on the phonon heat capacity.