Microwave dynamics of gated Al/InAs superconducting nanowires

TL;DR

This study investigates the microwave response and dynamic behavior of gate-tunable Al/InAs superconducting nanowires, revealing how gate voltage influences impedance and resonator properties, with implications for superconducting device design.

Contribution

It provides the first microwave characterization of gate-controlled InAs nanowires, demonstrating their impedance changes and response times, advancing understanding of their dynamic performance.

Findings

Resonator frequency shifts with gate voltage.

Internal losses increase as gate voltage varies.

Characteristic response times are around 40 ns.

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 superconducting logic. In particular, the suppression of the critical current as a function of the gate voltage has been widely investigated. However, 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 $\lambda/4$ coplanar waveguide resonator. We observe a shift in the resonator frequency and an increase in its internal losses as a function of the gate voltage, which we relate to a change in the imaginary and real components of the nanowire impedance, respectively. We demonstrate that these changes are described by the Mattis-Bardeen model with an effective temperature. We further study the resonator response to fast gate signals and measure characteristic response times of the order of 40 ns, both in time-domain and parametric modulation experiments. Our study elucidates the impact of the gate on the complex impedance of the nanowire in the superconducting state, as well as its dynamic performance, providing a foundation for the design of gate-controlled superconducting devices.