Microwave irradiation and quasiparticles in a superconducting double dot
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We study the interaction of the charge states of a superconducting double dot, comprising two superconducting islands coupled by a Josephson junction, with microwaves between 2 and 55 GHz. We observe resonant transitions between even-parity charge states at relatively low frequencies and breaking of Cooper pairs under higher-frequency irradiation, allowing our device to act as a click detector for microwave photons. By applying a magnetic field and tuning the pair-breaking energy, we perform spectroscopy on the environment in our cryostat and determine the temperature of a nonequilibrium photon bath. Finally, we exploit the band structure of our device to break Cooper pairs dependent on the symmetry of the initial Cooper pair state.
Lambert , N J , Esmail , A A , Pollock , F A , Edwards , M , Lovett , B W & Ferguson , A J 2017 , ' Microwave irradiation and quasiparticles in a superconducting double dot ' Physical Review. B, Condensed matter and materials physics , vol 95 , no. 23 , 235413 . DOI: 10.1103/PhysRevB.95.235413
Physical Review. B, Condensed matter and materials physics
© 2017, American Physical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at journals.aps.org / https://doi.org/10.1103/PhysRevB.95.235413
Funding: UK EPSRC EP/K025562.
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