Signatures of interactions in the Andreev spectrum of nanowire superconducting weak links

SPICE Workshop on Quantum Matter for Quantum Technologies, May 21st - May 23rd 2024

Marcelo Goffman

Quantronics Group, SPEC (CNRS), CEA-Saclay, Université Paris-Saclay, France
In a non-superconducting material linking two superconductors, discrete quasiparticles states are formed as electrons and holes are “transmuted” into each other through successive Andreev reflection processes at both interfaces. The energy of these Andreev bound states depends on the phase difference between the complex order parameters of the superconductors. As a result, such a “weak link” carries a supercurrent and behaves as an inductance that depends on the occupation of the Andreev states.
I will review a series of experiments performed on semiconducting nanowire weak links [1,2,3] relying on the techniques of “circuit Quantum Electrodynamics”, which consist in probing a quantum circuit through a coupled resonator [4]. They reveal the rich physics of Andreev Bound States, from the basics to the effects of spin-orbit coupling and of Coulomb interactions.

[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] 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).
[3] Signatures of interactions in the Andreev spectrum of nanowire Josephson junctions, F. J. Matute Cañadas, C. Metzger, Sunghun Park, L. Tosi, P. Krogstrup, J. Nygård, M. F. Goffman, C. Urbina, H. Pothier, A. Levy Yeyati, Phys. Rev. Lett. 128, 197702 (2022).
[4] 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).