Dark Optical Trapping of Resonant Transition-Metal Dichalcogenide Particles

Abstract

Mitigating recoil events and minimizing optically induced heating are central challenges in the precise control and cooling of macroscopic particles. To overcome this, we propose trapping resonant dielectric particles for applications in ultra-high vacuum (UHV) levitodynamics. Contrary to other approaches, where suppressing the parasitic resonant scattering was achieved in a standing wave geometry, here we propose a single beam geometry in a dark trap regime. As a promising material platform, we focus on a class of transition-metal dichalcogenide (TMD) particles with high polarizability, characterized by refractive indices in the range $3.7$-$4.8$ and densities up to $9.3~\mathrm{g\,cm^{-3}}$. Using full Mie theory, we identify a range of TMD particle radii that support stable axial and radial magnetic quadrupole trapping in a bottle-beam configuration. We predict that for WS$_2$ particles with a mass of $0.5 \times 10^{12}\,\mathrm{amu}$, one can expect suppression of the scattering rate relative to the mechanical frequency down to $\Gamma/\Omega \simeq 0.02$. This corresponds to a coherence time extended by approximately three orders of magnitude compared with silica particles of the same mass trapped in conventional bright optical traps at UHV. Combined with significantly reduced internal heating, remaining well below the melting point of the material, dark trapping of resonant TMD macroscopic particles emerges as a promising platform for exploring quantum physics with large masses.