Signatures of interactions in the Andreev spectrum of nanowire Josephson junctions (Part II)*

Hybrid semiconducting/superconducting nanostructures combined with circuit-QED techniques are allowing to explore superconducting proximity effects with an unprecedented degree of detail.  For instance, these techniques have permitted to reveal the fine structure, due to spin-orbit interactions, of Andreev states in semiconducting nanowire Josephson junctions [1]. While some of the observed features of the microwave spectrum could be explained in terms of few channels non-interacting models [1-3], other expected transitions lines from these models could not be clearly identified and some other experimental features remained unexplained.

In this work we show that the inclusion of electron-electron interactions is necessary to account for these unexplained features. This presentation, devoted to explain the theoretical approach, will be combined with the presentation by C. Metzger on the experimental results.

[1] Spin-Orbit Splitting of Andreev States Revealed by Microwave Spectroscopy, L. Tosi, C. Metzger, M. F. Goffman, C. Urbina, H. Pothier, Sunghun Park, A. Levy Yeyati, J. Nygård, and P. Krogstrup, Phys. Rev. X 9, 011010 (2019). 

[2] From Adiabatic to Dispersive Readout of Quantum Circuits, Sunghun Park, C. Metzger, L. Tosi, M. F. Goffman, C. Urbina, H. Pothier, and A. Levy Yeyati, Phys. Rev. Lett. 125, 077701 (2020)

[3] Circuit-QED with phase-biased Josephson weak links, C. Metzger, Sunghun Park, L. Tosi, C. Janvier, A. A. Reynoso, M. F. Goffman, C. Urbina, A. Levy Yeyati, and H. Pothier, Phys. Rev. Research 3, 013036 (2021)