AC-driven microwave loss modulation in a fluxonic metamaterial

TL;DR

This paper demonstrates a fluxonic metamaterial made of nanopatterned superconducting Nb microstrips that can modulate microwave loss levels using an ac drive, enabling tunable and quantized loss control for fluxonic devices.

Contribution

It introduces a novel fluxonic metamaterial with nanopatterned superconducting microstrips capable of controllably modulating microwave loss levels with an ac drive, including quantized loss synthesis.

Findings

Controllable modulation of $S_{21}(f)$ within 3 dB range.

Shape and duty cycle tuning of output signals based on groove symmetry.

Sine-to-triangular or sine-to-rectangular pulse conversion observed.

Abstract

We introduce a fluxonic metamaterial on the basis of nanopatterned superconducting Nb microstrips and employ it for modulation and synthesis of quantized loss levels in the lower GHz range by a sine-wave quasistatic ac drive. The nanopatterns are uniaxial nanogrooves with identical and different slope steepness, which induce a pinning potential of the washboard type for Abrikosov vortices. For the fundamental matching field, when the location of vortex rows geometrically matches the nanogrooves, the following effects are observed: The forward transmission coefficient $S_{21}(f)$ of the microstrips can be controllably modulated within a range of about $3$\,dB by the ac current. For the sample with symmetric grooves, depending on the choice of the operation point in the current-voltage curve, the shape and the duty cycle of the output signal can be tuned. For the sample with asymmetric grooves, depending on the ac amplitude, a sine-to-triangular or a sine-to-rectangular pulse shape conversion is observed. The possibility of synthesizing quantized loss levels by a serial connection of the two samples with different nanopatterns is exemplified and can be used for the development of multilevel excess-loss-based fluxonic devices.