Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 5: Superconductivity: Sample Preparation and Characterization

TT 5.1: Talk

Monday, March 9, 2026, 09:30–09:45, CHE/0089

Dielectric properties of NbN-films at the insulating side of the superconductor-insulator-transition — •Max Reinhart¹, Lea Pfaffinger¹, Sven Linzen², Evgenii Il’ichev², Alexander Weizel¹, and Christoph Strunk¹ — ¹Experimental and Applied Physics, Uni Regensburg, Germany — ²Leibniz Institute of Photonic Technology, Jena, Germany

In 2D strongly disordered thin films the superconductor-insulator-transition (SIT) occurs [1]. The resistive behavior of the insulating side of this transition is well studied, as it has been observed in various materials [2,3]. For the imaginary part of the impedance the situation is less clear. To obtain information on the dielectric properties of 3nm thin NbN in the insulating regime at R_sq(2 K)=60 kΩ we deposited interdigitated gold fingers as capacitor within an LC-circuit on SiOx and NbN. On SiOx, we obtained C≈6 pF. On insulating NbN, the measured capacitance was 6.6 pF. In the latter case the capacitance has a contribution, that depends non-monotonically on temperature, magnetic field and DC bias voltage.
[1] D.B. Haviland et al., Phys. Rev. Lett. 62 (1989) 2180
[2] V.F. Gantmakher and V.T. Dolgopolov, Phys. Usp. 180 (2010) 3
[3] N. G. Ebensperger, Dielectric properties on the insulating, side of the superconductor-insulator-transition [PhD thesis], Universität Stuttgart, 2021

Keywords: insulating NbN; disordered superconductor; superconductor insulator transition; capacitive response