Dysprosium dipolar Bose-Einstein condensate with broad Feshbach resonances

Abstract

We produce Bose-Einstein condensates of 162 Dy 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 s-wave character. Such resonances will ease the investigation of quantum phenomena relying on the interplay between dipole and contact interactions. 34.50.Cx, 37.0.De, 67.85.Hj Dipolar atomic Bose-Einstein condensates (dBEC) are proving to be excellent platforms for the study of a range of quantum phenomena relying on the interplay between the anisotropic long-range dipole-dipole interaction and the isotropic contact one. Recent experiments with dBEC demonstrated the existence of an unexpected quantum liquid phase, emerging for attractive mean-field interactions and stabilized by quantum fluctuations [1][2][3][4], showed the possibility to study lattice physics beyond the standard Bose-Hubbard model [5], and revealed first signatures of peculiar roton excitations [6] and scissors oscillations [7]. All these observations rely on the large magnetic moment available in Lanthanides, and require a fine control of the relative strength of dipolar and contact interactions. However, so far only very narrow Feshbach resonances, with widths of the order of tens of mG, have been employed to this scope. In fact, the complex electronic structure of such atoms, responsible for their large magnetic dipole moment, also leads to a strong anisotropy of the van der Waals interaction, which gives rise to an extremely dense chaotic distribution of narrow Feshbach resonances [8,9]. Dysprosium is the most magnetic atom available, whose magnetic dipole moment of 9.93 µ B results in a dipolar length a dd 130 a 0 . In the ground state of 164 Dy, besides the chaotic spectrum, two very broad Feshbach resonances with ∆ 30 G have been observed and characterized [10]. Their practical use is however questionable, since the resonances poles are surrounded by many narrow resonances. The other bosonic isotope, 162 Dy, has been characterized only up to 6 G: only narrow resonances appear, with the largest width around 25 mG [11,12].In this work we report on the production of a dBEC of 162 Dy and on the exploration of the resonance spec- * lucioni@lens.unifi.it trum up to 30 G. The BEC is produced employing a large-volume optical trap enhanced by an in-vacuum optical resonator, which allows an efficient capture of atoms from the magneto-optical trap (MOT) using a low-power single-mode laser. This technique was so far used only with alkalis and Yb atoms [13,14]; the application to dipolar Lanthanides is particularly intere...

Quantum chaos in Feshbach resonances of the ErYb system

“…In collisions of open-shell lanthanides with a non-zero orbital quantum number the spectrum is very dense: the anisotropic interaction potentials couple the magnetic Zeeman states with end-overend rotational quantum number, which results in multiple bound states being coupled to the entrance s-wave channel. Such a pattern was initially predicted by Kotochigova and Petrov [17,18], and confirmed experimentally for Er [9,19], and later for Dy atoms [20][21][22][23]. The resonance pattern is not only dense, but also features the characteristics of quantum chaos, evidenced by correlations in the resonance spacings.…”

Dilute dipolar quantum droplets beyond the extended Gross-Pitaevskii equation

“…Because of this we do not include this narrow resonance in our consideration of the scattering length. Additionally there is a broader resonance at B 3 = 21.95(5) G with a width of ∆B 3 = 2.4(8) G [50], that still has a small effect on the scattering length in the magnetic field range considered in this work. Using the mentioned resonances we can calculate the scattering length as a function of the magnetic field, with only the background scattering length as a free parameter ( Fig.…”

Production of a degenerate Fermi-Fermi mixture of dysprosium and potassium atoms

“…The key question, which we will have to answer in near-future experiments, is whether sufficiently broad Feshbach resonances exist to facilitate interaction tuning along with a suppression of inelastic losses. Reason for optimism is given by the fact that rather broad Feshbach resonances have been found in single-species experiments with Er and Dy [103][104][105].…”