Mechanical dissipation in MoRe superconducting metal drums

TL;DR

This study explores dissipation mechanisms in superconducting MoRe metal drums, revealing the role of two-level systems and how large amplitude driving suppresses mechanical dissipation, advancing understanding of damping in superconducting mechanical resonators.

Contribution

It provides experimental evidence of non-resonant TLSs affecting dissipation and demonstrates suppression of mechanical damping at high driving amplitudes in superconducting drums.

Findings

TLSs limit quality factor at low temperature

Large amplitude driving suppresses dissipation

Evidence for unconventional TLS saturation

Abstract

We experimentally investigate dissipation in mechanical resonators made of a disordered superconducting thin film of Molybdenum-Rhenium(MoRe) alloy. By electrostatically driving the drum with a resonant AC voltage, we detect its motion using a superconducting microwave cavity. From the temperature dependence of mechanical resonance frequencies and quality factors, we find evidence for non-resonant, mechanically active two-level systems (TLSs) limiting its quality factor at low temperature. In addition, we observe a strong suppression of mechanical dissipation at large mechanical driving amplitudes, suggesting an unconventional saturation of the non-resonant TLSs. These new observations shed light on the mechanism of mechanical damping in superconducting drums and routes towards understanding dissipation in such mechanical systems.