Orateur
Description
In 2D strongly disordered thin films the superconductor-insulator-transition (SIT) occurs [1]. The resistive behaviour 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. While it is known, that the superconducting side behaves inductive, we performed experiments on insulating highly disordered 3nm NbN films to investigate the other side of the transition. We applied an interdigital gold capacitor to the film, in which it functioned as dielectric medium. Measuring the resonance frequency of an otherwise known resonator, we found significant deviations from the expected geometric capacitance. We also find that the capacitance depends non-monotonically on temperature, magnetic field and bias voltage.
[1] D.B. Haviland et al., Phys. Rev. Lett. 62 2180 (1989)
[2] V.F. Gantmakher and V.T. Dolgopolov, Phys. Usp. 180, 3 (2010)
[3] N. G. Ebensperger, Dielectric propertiesontheinsulating, side ofthesuperconductor-insulator transition [PhD thesis], Universität Stuttgart, (2021)