Anisotropy-Induced Feshbach Resonances in a Quantum Dipolar Gas of Highly Magnetic Atoms

Abstract

We explore the anisotropic nature of Feshbach resonances in the collision between ultracold magnetic submerged-shell dysprosium atoms, which can only occur due to couplings to rotating bound states. This is in contrast to well-studied alkali-metal atom collisions, where most Feshbach resonances are hyperfine induced and due to rotation-less bound states. Our first-principle coupled-channel calculation of the collisions between spin-polarized bosonic dysprosium atoms reveals a striking correlation between the anisotropy in the magnetic dipole-dipole interaction and the anisotropy in the dispersion interaction. This latter anisotropy is absent in alkali-metal and chromium collisions. We show that both types of anisotropy significantly affect the Feshbach spectrum as a function of an external magnetic field. Effects of the electrostatic quadrupolequadrupole interaction are small. Over a 20 mT magnetic field range we predict about a ten Feshbach resonances and show that the resonance locations depend on the dysprosium isotope.A strongly interacting quantum gas of magnetic atoms, placed in an optical lattice, provides the opportunity to examine strongly correlated matter, creating a plat-form to explore exotic many-body phases known in solids, quantum ferrofluids, quantum liquid crystals, and supersolids [1,2]. Recent experimental advances [3][4][5][6][7][8][9][10] in trapping and cooling magnetic atoms pave the way towards these goals.In general, interactions between magnetic atoms are orientationally dependent or anisotropic. At room temperature anisotropic interactions are much smaller than kinetic energies and other major interactions between atoms, therefore can be ignored. The situation is different for an ultracold gas of atoms with a large magnetic moment. For example, the anisotropy due to magnetic dipole-dipole interactions between ultracold chromium atoms leads to an anisotropic deformation of a Bose Einstein condensate (BEC) [11]. Moreover, anisotropy plays a dominant role in collisional relaxation of ultracold atoms with large magnetic moments [5][6][7][12][13][14][15].

Spin-dependent collision of ultracold metastable atoms

“…In this respect, it is important to investigate the properties of collisions between the metastable triplet states and the ground state [16,17]. In addition, the study of anisotropically interacting cold collisions is now a broadening area of study and includes the rare-earth-metal atoms and polar molecules [18][19][20][21][22][23][24][25][26].…”

Classical Fractals and Quantum Chaos in Ultracold Dipolar Collisions

“…The recent work on ultracold collisions of highly magnetic atoms like lanthanides has shown a very dense spectrum of Fano-Feshbach resonances [18][19][20]. The statistics of nearest-neighbour spacings between resonances closely follow the WignerDyson distribution [20], which indicates that the corresponding classical dynamics may be chaotic after the Bohigas-Giannoni-Schmit (BGS) conjecture [21], therefore arousing further interest in quantum chaos of ultracold dipolar collisions [22][23][24][25][26][27][28].…”

Hubbard model for ultracold bosonic atoms interacting via zero-point-energy–induced three-body interactions

“…Recently, interest has also focused on resonances with atoms with large magnetic moments, such as Cr [50], Er [51], and Dy [52,53], as the long-range magnetic dipole-dipole interaction influences their collective behavior.…”