We show that for ultracold magnetic lanthanide atoms chaotic scattering emerges due to a combination of anisotropic interaction potentials and Zeeman coupling under an external magnetic field. This scattering is studied in a collaborative experimental and theoretical effort for both dysprosium and erbium. We present extensive atom-loss measurements of their dense magnetic Feshbach-resonance spectra, analyze their statistical properties, and compare to predictions from a random-matrix-theory-inspired model. Furthermore, theoretical coupled-channels simulations of the anisotropic molecular Hamiltonian at zero magnetic field show that weakly bound, near threshold diatomic levels form overlapping, uncoupled chaotic series that when combined are randomly distributed. The Zeeman interaction shifts and couples these levels, leading to a Feshbach spectrum of zero-energy bound states with nearest-neighbor spacings that changes from randomly to chaotically distributed for increasing magnetic field. Finally, we show that the extreme temperature sensitivity of a small, but sizable fraction of the resonances in the Dy and Er atom-loss spectra is due to resonant nonzero partial-wave collisions. Our threshold analysis for these resonances indicates a large collision-energy dependence of the three-body recombination rate.We show that for ultracold magnetic lanthanide atoms chaotic scattering emerges due to a combination of anisotropic interaction potentials and Zeeman coupling under an external magnetic field. This scattering is studied in a collaborative experimental and theoretical effort for both dysprosium and erbium. We present extensive atom-loss measurements of their dense magnetic Feshbach-resonance spectra, analyze their statistical properties, and compare to predictions from a random-matrix-theory-inspired model. Furthermore, theoretical coupled-channels simulations of the anisotropic molecular Hamiltonian at zero magnetic field show that weakly bound, near threshold diatomic levels form overlapping, uncoupled chaotic series that when combined are randomly distributed. The Zeeman interaction shifts and couples these levels, leading to a Feshbach spectrum of zero-energy bound states with nearest-neighbor spacings that changes from randomly to chaotically distributed for increasing magnetic field. Finally, we show that the extreme temperature sensitivity of a small, but sizable fraction of the resonances in the Dy and Er atom-loss spectra is due to resonant nonzero partial-wave collisions. Our threshold analysis for these resonances indicates a large collision-energy dependence of the three-body recombination rate.

arXiv:1506.05221Physical Review XNov 19, 2015127 citations

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

Milan Krstajić, Péter Juhász, Jiří Kučera +4 more

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.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.

arXiv:2307.01245Physical Review ADec 1, 202310 citations

Ultracold dynamics of magnetic dipolar molecules

Goulven Quéméner, Maxence Lepers, Jean-François Wyart +1 more

Bulletin of the American Physical SocietyJun 6, 20130 citations

^{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.