Simulation of sympathetic cooling an optically levitated magnetic nanoparticle via coupling to a cold atomic gas

TL;DR

This paper proposes a theoretical scheme for sympathetically cooling a magnetic nanoparticle using a cold atomic gas via magnetic dipole interactions, demonstrating potential for effective cooling surpassing existing methods.

Contribution

It introduces a novel sympathetic cooling method for magnetic nanoparticles through atom-gas coupling, with detailed simulations showing its effectiveness and scalability.

Findings

Cooling rate depends on atom species and system parameters.

Simulated damping rates can surpass traditional cooling methods.

Linear interaction potential enables energy exchange between nanoparticle and atoms.

Abstract

A proposal for cooling the translational motion of optically levitated magnetic nanoparticles is presented. The theoretical cooling scheme involves the sympathetic cooling of a ferromagnetic YIG nanosphere with a spin-polarized atomic gas. Particle-atom cloud coupling is mediated through the magnetic dipole-dipole interaction. When the particle and atom oscillations are small compared to their separation, the interaction potential becomes dominantly linear which allows the particle to exchange energy with the $N$ atoms. While the atoms are continuously Doppler cooled, energy is able to be removed from the nanoparticle's motion as it exchanges energy with the atoms. The rate at which energy is removed from the nanoparticle's motion was studied for three species of atoms (Dy, Cr, Rb) by simulating the full $N+1$ equations of motion and was found to depend on system parameters with scalings that are consistent with a simplified model. The nanoparticle's damping rate due to sympathetic cooling is competitive with and has the potential to exceed commonly employed cooling methods.