Publication on new types of materials for magnetic levitation and feedback cooling!

Working with international colleagues in Tawian and Australia we have developed a new type of diamagnetic material which experiences virtually no eddy damping when it moves through intense magnetic fields. When we magnetically levitate this material using strong magnets and evacuate all the air - the object is so undamped that when it is motionally excited (a small tap on the optical table), it vibrates for almost a DAY - before it settles down again. This makes the motion of such an object extremely sensitive - perfect for use as an extreme sensor. However, the motion of the object at room temperature is quite large due to thermal excitations and this motional noise degrades the performance of such a sensor. So we have developed feedback cooling of the motion of the object - where we quickly measure (in real time), the position and velocity of the object and (in real time), apply forces on it to slow its motion. With ultra-fast signal processing (using a field programmable gate array), we are able to reduce its motional tempature by three orders of magnitude. This is an important step on our route towards ultra-sensitive inertial sensors and towards the quantum regime of motion via magnetic levitation.

The results have been published in Applied Physics Letters [Appl. Phys. Lett. 124, 124002 (2024)], and are OPEN ACCESS.