arXiv subjects

Frankie Fung

Publications and source records attributed to Frankie Fung.

4 recordsLinked to original sources

arXiv2026

Nonlinear dynamics and mechanical frequency combs with a Meissner-levitated micromagnet

Nonlinearities in multimode mechanical systems can give rise to rich dynamical phenomena with great potential for sensing applications and for future quantum experiments. We demonstrate that the coupled center-of-mass and rotational motion of a Meissner-levitated micromagnet offer a promising platform for nonlinear dynamics, combining low dissipation, magnetic tunability, strong intrinsic Duffing nonlinearities, and nonlinear intermodal couplings. We use this tunability to demonstrate the generation of a mechanical frequency comb in the micromagnet dynamics, realized by parametric excitation of two translational modes followed by cascaded nonlinear frequency mixing, which produces a phononic comb with tunable spacing. At large amplitudes, nonlinear coupling to a low-frequency librational mode of the magnet leads to parametric excitation and phase locking of that mode, generating a dense spectral fine structure at subharmonics of the drive. These results establish levitated micromagnets as a platform for nonlinear multimode mechanics, with potential applications in precision sensing and quantum-limited metrology.

quant-ph↗

arXiv2026

Exploring dynamics of individual vortices in a superconductor via a levitated magnetic transducer

Trapped vortices determine fundamental properties of superconductors and play an important role in many practical applications such as magnetic levitation, however their complex dynamics remain poorly understood. Here, we use the mechanical motion of micron-scale levitated magnetic particles to probe the dynamics of individual vortices. Specifically, we show that the dynamics of levitated magnets are strongly influenced by vortices trapped in the YBCO superconducting film. We observe random telegraph signals in the mechanical frequency, dissipation rate, and energy of levitated particles, which we attribute to random tunneling of individual vortices. The nonlinearity of vortex-defect interaction manifests as non-exponential decay in ringdown measurements, revealing a complex underlying potential landscape. Our results provide insights into elusive dissipation mechanisms in superconducting levitated systems, open new avenues for using levitated magnets as sensitive probes of static and dynamic properties of individual vortices in superconductors and their interactions with material disorder, and point toward novel routes for using magnetic particles as highly coherent mechanical transducers.

quant-ph↗

arXiv2017

Dynamics and interactions of particles in a thermophoretic trap

We investigate dynamics and interactions of particles levitated and trapped by the thermophoretic force in a vacuum cell. Our analysis is based on footage taken by orthogonal cameras that are able to capture the three dimensional trajectories of the particles. In contrast to spherical particles, which remain stationary at the center of the cell, here we report new qualitative features of the motion of particles with non-spherical geometry. Singly levitated particles exhibit steady spinning around their body axis and rotation around the symmetry axis of the cell. When two levitated particles approach each other, repulsive or attractive interactions between the particles are observed. Our levitation system offers a wonderful platform to study interaction between particles in a microgravity environment.

cond-mat.soft↗

arXiv2016

Stable thermophoretic trapping of generic particles at low pressures

We demonstrate levitation and three-dimensionally stable trapping of a wide variety of particles in a vacuum chamber through the use of the thermophoretic force in the presence of a strong temperature gradient. Typical sizes of the trapped particles are between 10 microns and 1 mm at a pressure between 1 and 10 Torr. The trapping stability is provided by the geometry of the temperature field, as well as the transition between the free molecule and hydrodynamic regimes of the thermophoretic force. To quantitatively measure the thermophoretic force, we examine the levitation heights of spherical polyethylene spheres under various experimental conditions and determine the temperature gradient needed to levitate the particles. A good agreement between our experimental observations and theoretical calculations is obtained. Our system offers a new platform to study thermophoretic phenomena and to simulate dynamics of interacting many-body systems in a microgravity environment.

cond-mat.soft↗