High-Q Diamagnetically Levitated Mechanical Resonators with Time-Domain Ring-Down Measurements

We report on experiments and simulations of centimeter-scale composite plate resonators diamagnetically levitated over permanent magnets, with carefully engineered graphite particles and dielectric constituents in the composite. Two devices with masses of 34 mg and 727 mg are fabricated, and their resonance behaviors are characterized in both frequency and time domains. The 34 mg device, with well-isolated graphite particles, exhibits multiple resonance modes at 18.1 Hz, 18.6 Hz, and 20.4 Hz. Using time-domain ring-down techniques, we obtain quality (Q) factor of Q≈33000 at 0.6 mTorr, compared to Q≈1400 at 10 mTorr and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex> ≈7 at atmospheric pressure, showing the dominant role of air damping in limiting <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex>. To investigate eddy current damping, we fabricate a larger device (mass of 727 mg) with more agglomerated graphite particles inside the dielectric material, increasing the effective graphite particle sizes. The agglomerated graphite distribution led to increased eddy current losses and a significantly lower <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex> of 240, elucidating the critical role of composite homogeneity. These results advance the understanding of dissipation mechanisms in levitated resonators and inform the design of high-Q platforms for precision sensing and levitation-based technologies.