Vittorio Buccheri, Quantum Device Physics Laboratory

Abstract: Several experiments have recently reported on gate-tunable superconducting properties in metallic devices, holding promise for the realization of cryogenic switches, tunable resonators, and super-conducting logic. However, a clear understanding of the mechanisms enabling gate control is still missing. Moreover, while the static characterization of this phenomenon, namely the suppression of the critical current as a function of the gate voltage, is widely investigated in different configurations and materials, time-domain studies are discussed only in a few cases. In this paper, we present a microwave characterization of a gate-controlled Al-capped InAs nanowire embedded in a λ/4 coplanar waveguide resonator. We observe a shift in the resonator frequency and an increase in the internal losses due to the gate’s influence on the imaginary and real components of the nanowire impedance, respectively. We demonstrate that our experiments can be described by the Mattis-Bardeen model with an effective temperature approach. Also, we measure characteristic response times on the order of 40 ns, both in time-domain and parametric modulation experiments. Our findings contribute to our understanding of the impact of the gate on the nanowire impedance and give an insight on the dynamic performance of gate-controlled superconducting devices.

Main supervisor: Simone Gasparinetti, Associate Professor
Examiner: Mikael Fogelström, Professor
Supervisor: Thilo Bauch, Associate Professor

Discussion leader: Giovanna Sammarco Tancredi, Senior Researcher