Microwave response of a metallic superconductor subject to a high-voltage gate electrode

Giacomo Catto (Corresponding Author), Wei Liu (Corresponding Author), Suman Kundu, Valtteri Lahtinen, Visa Vesterinen, Mikko Möttönen

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)


Processes that lead to the critical-current suppression and change of impedance of a superconductor under the application of an external voltage is an active area of research, especially due to various possible technological applications. In particular, field-effect transistors and radiation detectors have been developed in the recent years, showing the potential for precision and sensitivity exceeding their normal-metal counterparts. In order to describe the phenomenon that leads to the critical-current suppression in metallic superconducting structures, a field-effect hypothesis has been formulated, stating that an electric field can penetrate the metallic superconductor and affect its characteristics. The existence of such an effect would imply the incompleteness of the underlying theory, and hence indicate an important gap in the general comprehension of superconductors. In addition to its theoretical value, a complete understanding of the phenomenon underneath the electric-field response of the superconductor is important in the light of the related technological applications. In this paper, we study the change of the characteristics of a superconductor implementing a coplanar-waveguide resonator as a tank circuit, by relating our measurements to the reactance and resistance of the material. Namely, we track the state of the superconductor at different voltages and resulting leakage currents of a nearby gate electrode which is not galvanically connected to the resonator. By comparing the effects of the leakage current and of a change in the temperature of the system, we conclude that the observed behaviour in the superconductor is mainly caused by the heat that is deposited by the leakage current, and bearing the experimental uncertainties, we are not able to observe the effect of the applied electric field in our sample. In addition, we present a relatively good quantitative agreement between the Mattis–Bardeen theory of a heated superconductor and the experimental observations. Importantly, we do not claim this work to nullify the results of previous works, but rather to provide inspiration for future more thorough experiments and analysis using the methods presented here.

Original languageEnglish
Article number6822
JournalScientific Reports
Issue number1
Publication statusPublished - 26 Apr 2022
MoE publication typeA1 Journal article-refereed


We have received funding from European Research Council under Grant No?681311 (QUESS) and Academy of Finland through its Centres of Excellence Programme (project numbers 312300, 312295 and 336819) and Grants (numbers 314449, 321700 and 335460). We thank Yuri Pashkin for useful discussions.


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