Diamagnetically levitated force sensor with adjustable natural frequency between 0.5 and 21 Hz

Diamagnetically levitated resonators of milligram and sub-milligram scale are emerging as an advantageous force measurement system. Force sensors with low and adjustable frequencies are essential for gravimeter and for the search of ultralight dark matter in the low-energy domain. Here, we propose and experimentally demonstrate a diamagnetically levitated force sensor capable of efficiently and robustly tuning its natural frequency between 0.5 and 21 Hz theoretically. We show that by altering the geometric structure of the magnet setup and the force sensor, especially the gap between two layers of magnets, we can effectively control the potential gradient of the magneto-gravitational trap, which allows us to continuously tune the natural frequency of the force sensor down to 0.5 Hz. We have experimentally demonstrated the effectiveness of this design scheme at room temperature. This robust frequency-tuning diamagnetically levitated force sensor may provide a promising platform for studying a broad field of fundamental physics.