Ground-state phase diagram and parity-flipping microwave transitions in a gate-tunable Josephson junction

M. R. Sahu; F. J. Matute-Cañadas; M. Benito; P. Krogstrup; J. Nygård; M. F. Goffman; C. Urbina; A. Levy Yeyati; H. Pothier

doi:10.1103/PhysRevB.109.134506

Ground-state phase diagram and parity-flipping microwave transitions in a gate-tunable Josephson junction

M. R. Sahu, F. J. Matute-Cañadas, M. Benito, P. Krogstrup, J. Nygård, M. F. Goffman, C. Urbina, A. Levy Yeyati, H. Pothier

DOI 10.1103/PhysRevB.109.134506 · Physical Review B

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Abstract

We probed a gate-tunable InAs nanowire Josephson weak link by coupling it to a microwave resonator. Tracking the resonator frequency shift when the weak link is close to pinch-off, we observe that the ground state of the latter alternates between a singlet and a doublet when varying either the gate voltage or the superconducting phase difference across it. The corresponding microwave absorption spectra display lines that approach zero energy close to the singlet-doublet boundaries, suggesting parity-flipping transitions, which are in principle forbidden in microwave spectroscopy and expected to arise only in tunnel spectroscopy. We tentatively interpret them by means of an ancillary state isolated in the junction acting as a reservoir for individual electrons.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
InAs Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
NbTiN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown