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arXiv · 2511.14313

Full Shapiro spectroscopy of current-phase relationships

Maxim Tjøtta·Devashish Shah·Kanishk Modi·Marco Valentini·Rubén Seoane Souto·Georgios Katsaros·Jeroen Danon
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Abstract

Extracting the current-phase relationship (CPR) of a single superconducting junction is challenging in practice and traditionally involves embedding the junction in a larger superconducting circuit containing SQUIDs and/or resonators. Applying ac driving to the junction has proven to be a viable and less invasive way to extract information about the few lowest harmonics of the CPR, by locating the integer and fractional Shapiro steps in the IV-curve of the driven junction. Here, we present an alternative driving-based method that allows to extract the full harmonic content of a CPR in a non-invasive way, by fitting the measured critical currents of the driven junction as a function of driving power. We test our method, both using numerical simulations and in experiments, and we show that it works very accurately, also in the presence of noise.

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Maxim Tjøtta, Devashish Shah, Kanishk Modi, Marco Valentini, Rubén Seoane Souto, Georgios Katsaros, Jeroen Danon. 2025-11-18. Full Shapiro spectroscopy of current-phase relationships. https://arxiv.org/abs/2511.14313

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