%0 Journal Article %D 2019 %T Feshbach resonances in p-wave three-body recombination within Fermi-Fermi mixtures of open-shell 6Li and closed-shell 173Yb atoms %A Alaina Green %A Hui Li %A Jun Hui See Toh %A Xinxin Tang %A Katherine McCormick %A Ming Li %A Eite Tiesinga %A Svetlana Kotochigova %A Subhadeep Gupta %X

We report on observations and modeling of interspecies magnetic Feshbach resonances in dilute ultracold mixtures of open-shell alkali-metal 6Li and closed-shell 173Yb atoms with temperatures just above quantum degeneracy for both fermionic species. Resonances are located by detecting magnetic-field-dependent atom loss due to three-body recombination. We resolve closely-located resonances that originate from a weak separation-dependent hyperfine coupling between the electronic spin of 6Li and the nuclear spin of 173Yb, and confirm their magnetic field spacing by ab initio electronic-structure calculations. Through quantitative comparisons of theoretical atom-loss profiles and experimental data at various temperatures between 1 μK and 20 μK, we show that three-body recombination in fermionic mixtures has a p-wave Wigner threshold behavior leading to characteristic asymmetric loss profiles. Such resonances can be applied towards the formation of ultracold doublet ground-state molecules and quantum simulation of superfluid p-wave pairing.

%8 12/10/2019 %G eng %U https://arxiv.org/abs/1912.04874 %0 Journal Article %J Science Advances %D 2018 %T Fractal Universality in Near-Threshold Magnetic Lanthanide Dimers %A Constantinos Makrides %A Ming Li %A Eite Tiesinga %A Svetlana Kotochigova %X

Ergodic quantum systems are often quite alike, whereas nonergodic, fractal systems are unique and display characteristic properties. We explore one of these fractal systems, weakly bound dysprosium lanthanide molecules, in an external magnetic field. As recently shown, colliding ultracold magnetic dysprosium atoms display a soft chaotic behavior with a small degree of disorder. We broaden this classification by investigating the generalized inverse participation ratio and fractal dimensions for large sets of molecular wave functions. Our exact close-coupling simulations reveal a dynamic phase transition from partially localized states to totally delocalized states and universality in its distribution by increasing the magnetic field strength to only a hundred Gauss (or 10 mT). Finally, we prove the existence of nonergodic delocalized phase in the system and explain the violation of ergodicity by strong coupling between near-threshold molecular states and the nearby continuum.

%B Science Advances %V 4 %P eaap8308 %8 2018/02/16 %G eng %U https://arxiv.org/abs/1802.09586 %N 2 %R https://doi.org/10.1126/sciadv.aap8308 %0 Journal Article %D 2018 %T Orbital quantum magnetism in spin dynamics of strongly interacting magnetic lanthanide atoms %A Ming Li %A Eite Tiesinga %A Svetlana Kotochigova %X

Laser cooled lanthanide atoms are ideal candidates with which to study strong and unconventional quantum magnetism with exotic phases. Here, we use state-of-the-art closed-coupling simulations to model quantum magnetism for pairs of ultracold spin-6 erbium lanthanide atoms placed in a deep optical lattice. In contrast to the widely used single-channel Hubbard model description of atoms and molecules in an optical lattice, we focus on the single-site multi-channel spin evolution due to spin-dependent contact, anisotropic van der Waals, and dipolar forces. This has allowed us to identify the leading mechanism, orbital anisotropy, that governs molecular spin dynamics among erbium atoms. The large magnetic moment and combined orbital angular momentum of the 4f-shell electrons are responsible for these strong anisotropic interactions and unconventional quantum magnetism. Multi-channel simulations of magnetic Cr atoms under similar trapping conditions show that their spin-evolution is controlled by spin-dependent contact interactions that are distinct in nature from the orbital anisotropy in Er. The role of an external magnetic field and the aspect ratio of the lattice site on spin dynamics is also investigated.

%G eng %U https://arxiv.org/abs/1804.10102 %0 Journal Article %J Physical Review Letters %D 2012 %T Anisotropy induced Feshbach resonances in a quantum dipolar gas of magnetic atoms %A Alexander Petrov %A Eite Tiesinga %A Svetlana Kotochigova %X 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 novel first-principle coupled-channel calculation of the collisions between open-4f-shell spin-polarized bosonic dysprosium reveals a striking correlation between the anisotropy due to magnetic dipole-dipole and electrostatic interactions and the Feshbach spectrum as a function of an external magnetic field. Over a 20 mT magnetic field range we predict about a dozen Feshbach resonances and show that the resonance locations are exquisitely sensitive to the dysprosium isotope. %B Physical Review Letters %V 109 %8 2012/9/7 %G eng %U http://arxiv.org/abs/1203.4172v1 %N 10 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.109.103002 %0 Journal Article %J New Journal of Physics %D 2009 %T Multi-channel modelling of the formation of vibrationally cold polar KRb molecules %A Svetlana Kotochigova %A Eite Tiesinga %A Paul S. Julienne %X We describe the theoretical advances that influenced the experimental creation of vibrationally and translationally cold polar $^{40}$K$^{87}$Rb molecules \cite{nphys08,science08}. Cold molecules were created from very-weakly bound molecules formed by magnetic field sweeps near a Feshbach resonance in collisions of ultra-cold $^{40}$K and $^{87}$Rb atoms. Our analysis include the multi-channel bound-state calculations of the hyperfine and Zeeman mixed X$^1\Sigma^+$ and a$^3\Sigma^+$ vibrational levels. We find excellent agreement with the hyperfine structure observed in experimental data. In addition, we studied the spin-orbit mixing in the intermediate state of the Raman transition. This allowed us to investigate its effect on the vibrationally-averaged transition dipole moment to the lowest ro-vibrational level of the X$^1\Sigma^+$ state. Finally, we obtained an estimate of the polarizability of the initial and final ro-vibrational states of the Raman transition near frequencies relevant for optical trapping of the molecules. %B New Journal of Physics %V 11 %P 055043 %8 2009/05/14 %G eng %U http://arxiv.org/abs/0901.1486v1 %N 5 %! New J. Phys. %R 10.1088/1367-2630/11/5/055043 %0 Journal Article %J Physical Review Letters %D 2003 %T Ultracold collision properties of metastable alkaline-earth atoms %A Andrei Derevianko %A Sergey G. Porsev %A Svetlana Kotochigova %A Eite Tiesinga %A Paul S. Julienne %X Ultra-cold collisions of spin-polarized 24Mg,40Ca, and 88Sr in the metastable 3P2 excited state are investigated. We calculate the long-range interaction potentials and estimate the scattering length and the collisional loss rate as a function of magnetic field. The estimates are based on molecular potentials between 3P2 alkaline-earth atoms obtained from ab initio atomic and molecular structure calculations. The scattering lengths show resonance behavior due to the appearance of a molecular bound state in a purely long-range interaction potential and are positive for magnetic fields below 50 mT. A loss-rate model shows that losses should be smallest near zero magnetic field and for fields slightly larger than the resonance field, where the scattering length is also positive. %B Physical Review Letters %V 90 %8 2003/2/13 %G eng %U http://arxiv.org/abs/physics/0210076v1 %N 6 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.90.063002