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arXiv:2307.01245 · Physical Review A

Characterization of three-body loss in Er166 and optimized production of large Bose-Einstein condensates

Milan Krstajić, Péter Juhász, Jiří Kučera, Lucas R. Hofer, G. Lamb, A. L. Marchant, Robert P. Smith

Published Dec 1, 2023• 10 citations
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Abstract

Ultracold gases of highly magnetic lanthanide atoms have enabled the realization of dipolar quantum droplets and supersolids. However, future studies could be limited by the achievable atom numbers and hindered by high three-body loss rates. Here we study density-dependent atom loss in an ultracold gas of $^{166}\mathrm{Er}$ for magnetic fields below 4 G, identifying six previously unreported, strongly temperature-dependent features. We find that their positions and widths show a linear temperature dependence up to at least $15\phantom{\rule{0.16em}{0ex}}\textmu{}\mathrm{K}$. In addition, we observe a weak, polarization-dependent shift of the loss features with the intensity of the light used to optically trap the atoms. This detailed knowledge of the loss landscape allows us to optimize the production of dipolar Bose-Einstein condensates with more than $2\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms and points towards optimal strategies for the study of large-atom-number dipolar gases in the droplet and supersolid regimes.

DOI
10.1103/physreva.108.063301

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Loss features in ultracold 162^{162}162Dy gases: two- versus three-body processes
Dipolar gases like erbium and dysprosium have a dense spectrum of resonant loss features associated with their strong anisotropic interaction potential. These resonances display various behaviours with density and temperature, implying diverse microscopic properties. Here, we quantitatively investigate the low-field (B<6 GB < 6\,\text{G}B<6G) loss features in ultracold thermal samples of 162^{162}162Dy, revealing two- and three-body dominated loss processes. We investigate their temperature dependence and detect a feature compatible with a ddd-wave Fano-Feshbach resonance, which has not been observed before. We also analyse the expansion of the dipolar Bose-Einstein condensate as a function of the magnetic field and interpret the changes in size close to the resonances with a variation in the scattering length.
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We numerically study the many-body physics of molecular Bose-Einstein condensates with strong dipole-dipole interactions. We observe the formation of self-bound droplets, and explore phase diagrams that feature a variety of exotic supersolid states. In all of these cases, the large and tunable molecular dipole moments enable the study of unexplored regimes and phenomena, including liquidlike density saturation and universal stability scaling laws for droplets, as well as pattern formation and the limits of droplet supersolidity. We discuss a realistic experimental approach to realize both the required collisional stability of the molecular gases and the independent tunability of their contact and dipolar interaction strengths. Our work provides both a blueprint and a benchmark for near-future experiments with bulk molecular Bose-Einstein condensates.
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We produce Bose-Einstein condensates of 162Dy^{162}\mathrm{Dy}162Dy atoms employing an innovative technique based on a resonator-enhanced optical trap that allows efficient loading from the magneto-optical trap. We characterize the scattering properties of the ultracold atoms for magnetic fields between 6 and 30 G. In addition to the typical chaotic distribution of narrow Feshbach resonances in lanthanides, we discover two rather isolated broad features at around 22 G and 27 G. A characterization using the complementary measurements of losses, thermalization, anisotropic expansion, and molecular binding energy points towards resonances of predominant sss-wave character. Such resonances will ease the investigation of quantum phenomena relying on the interplay between dipole and contact interactions.