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TT: Fachverband Tiefe Temperaturen

TT 5: Superconductivity: Properties and Electronic Structure I

TT 5.4: Talk

Monday, March 17, 2025, 10:15–10:30, H36

Local limit disorder characteristics of superconducting radio frequency cavities I. Frequency shift — •Matúš Hladký, Anastasiya Lebedeva, Marcel Polák, and František Herman — Comenius University in Bratislava

Negative resonant frequency shift abnormalities in the vicinity of the critical temperature have been observed in recent experiments on Superconducting Radio Frequency cavities.

We present a simple, straightforward approach using the Dynes superconductor theory [1] and discuss its results. In the ideal dirty limit, we analytically elaborate on the width and depth of the resulting dip. Studying the sign of the slope of the resonant frequency shift at crit. temperature in the moderately clean regime reveals the role of the pair-breaking and pair-conserving disorder. Next, we compare and also fit our results with the recent experimental data from the N-doped Nb sample presented in Ref. [2]. Our analysis remarkably complies with the experimental findings, especially concerning the dip width. We offer straightforward, homogeneous-disorder-based interpretation within the moderately clean regime.

This work has been supported by the APVV-23-0515 grant and by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 945478.

[1] A. Lebedeva, M. Hladký, M. Polák, F. Herman, arXiv:2409.04203v1.

[2] M. Zarea, H. Ueki, J. A. Sauls, Frontiers in Superconducting Materials, 3: 1-7, arXiv:2307.07905v1 (2023).

Keywords: Frequency shift; pair-breaking disorder; pair-conserving disorder; superconducting cavities; Local limit electromagnetic response