Ultralow mechanical damping with Meissner-levitated ferromagnetic microparticles

TL;DR

This paper demonstrates ultralow mechanical damping in Meissner-levitated ferromagnetic microparticles, achieving extremely high quality factors and damping times, which enhances their potential for sensitive sensing and quantum physics applications.

Contribution

The study provides the first experimental evidence of ultralow damping in Meissner-levitated ferromagnetic microspheres, with damping times exceeding 10,000 seconds and quality factors over 10 million.

Findings

Measured damping times $ au$ > 10^4 seconds

Achieved quality factors $Q$ > 10^7

Observed modes agree with theoretical models

Abstract

Levitated nanoparticles and microparticles are excellent candidates for the realization of extremely isolated mechanical systems, with a huge potential impact in sensing applications and in quantum physics. Magnetic levitation based on static fields is a particularly interesting approach, due to the unique property of being completely passive and compatible with low temperatures. Here, we show experimentally that micromagnets levitated above type-I superconductors feature very low damping at low frequency and low temperature. In our experiment, we detect 5 out of 6 rigid-body mechanical modes of a levitated ferromagnetic microsphere, using a dc SQUID (Superconducting Quantum Interference Device) with a single pick-up coil. The measured frequencies are in agreement with a finite element simulation based on ideal Meissner effect. For two specific modes we find further substantial agreement with analytical predictions based on the image method. We measure damping times $\tau$ exceeding $10^4$ s and quality factors $Q$ beyond $10^7$, improving by $2-3$ orders of magnitude over previous experiments based on the same principle. We investigate the possible residual loss mechanisms besides gas collisions, and argue that much longer damping time can be achieved with further effort and optimization. Our results open the way towards the development of ultrasensitive magnetomechanical sensors with potential applications to magnetometry and gravimetry, as well as to fundamental and quantum physics.