Microwave Susceptibility Observation of Interacting Many-Body Andreev States
V. Fatemi (Yale University)
P. D. Kurilovich (Yale University)
M. Hays (Yale University)
D. Bouman (TU Delft - BUS/Quantum Delft, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
T. Connolly (Yale University)
S. Diamond (Yale University)
P. Krogstrup (University of Copenhagen)
A. Geresdi (TU Delft - QRD/Geresdi Lab, Chalmers University of Technology, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
M. H. Devoret (Yale University)
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Abstract
Electrostatic charging affects the many-body spectrum of Andreev states, yet its influence on their microwave properties has not been elucidated. We developed a circuit quantum electrodynamics probe that, in addition to transition spectroscopy, measures the microwave susceptibility of different states of a semiconductor nanowire weak link with a single dominant (spin-degenerate) Andreev level. We found that the microwave susceptibility does not exhibit a particle-hole symmetry, which we qualitatively explain as an influence of Coulomb interaction. Moreover, our state-selective measurement reveals a large, ?-phase shifted contribution to the response common to all many-body states which can be interpreted as arising from a phase-dependent continuum in the superconducting density of states.