Suppression of damping in a diamagnetically levitated dielectric sphere via eddy currents and static charge reduction

Diamagnetically levitated micro-nano oscillators play a crucial role in fundamental physics research and the advancement of high-precision sensors. Achieving high sensitivity in acceleration or force sensing is a fundamental requirement within these research domains. The primary limitation in achieving such sensitivity is thermal noise, which is directly proportional to the motion damping of the oscillator. Theoretical modeling suggests the presence of significant damping mechanisms induced by eddy currents. In this study, we validated the theoretical model by optimizing the structure of the magnet trap, confirming the impact of eddy currents on the damping of the oscillators. Additionally, we observed another type of damping caused by static charge in moving levitated dielectrics. Subsequently, we proposed an innovative theoretical model to explain this phenomenon and verified its validity during the charge neutralization process. Through these efforts, we successfully reduced the total damping from 1.6 mHz to 0.15 mHz, resulting in an order of magnitude improvement in performance. Our sensing system achieved the highest sensitivity of acceleration sensing in diamagnetically levitated submillimeter-scale dielectric to date, measuring 7.6±0.8)×10^-10g/Hz. The exploration conducted in this study regarding the analysis and suppression of electromagnetic damping, along with associated thermal noise, holds significant promise for frontier research involving sensing with levitating dielectrics.