@article {2535, title = {Feshbach resonances in p-wave three-body recombination within Fermi-Fermi mixtures of open-shell 6Li and closed-shell 173Yb atoms}, year = {2019}, month = {12/10/2019}, abstract = {

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.

}, url = {https://arxiv.org/abs/1912.04874}, author = {Alaina Green and Hui Li and Jun Hui See Toh and Xinxin Tang and Katherine McCormick and Ming Li and Eite Tiesinga and Svetlana Kotochigova and Subhadeep Gupta} } @article {2304, title = {Fractal Universality in Near-Threshold Magnetic Lanthanide Dimers}, journal = {Science Advances}, volume = {4}, year = {2018}, month = {2018/02/16}, pages = {eaap8308}, abstract = {

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.

}, doi = {https://doi.org/10.1126/sciadv.aap8308}, url = {https://arxiv.org/abs/1802.09586}, author = {Constantinos Makrides and Ming Li and Eite Tiesinga and Svetlana Kotochigova} } @article {1273, title = {Formation and decay of Bose-Einstein condensates in an excited band of a double-well optical lattice }, journal = {Physical Review A}, volume = {88}, year = {2013}, month = {2013/9/12}, abstract = { We study the formation and collision-aided decay of an ultra-cold atomic Bose-Einstein condensate in the first excited band of a double-well 2D-optical lattice with weak harmonic confinement in the perpendicular $z$ direction. This lattice geometry is based on an experiment by Wirth et al. The double well is asymmetric, with the local ground state in the shallow well nearly degenerate with the first excited state of the adjacent deep well. We compare the band structure obtained from a tight-binding (TB) model with that obtained numerically using a plane wave basis. We find the TB model to be in quantitative agreement for the lowest two bands, qualitative for next two bands, and inadequate for even higher bands. The band widths of the excited bands are much larger than the harmonic oscillator energy spacing in the $z$ direction. We then study the thermodynamics of a non-interacting Bose gas in the first excited band. We estimate the condensate fraction and critical temperature, $T_c$, as functions of lattice parameters. For typical atom numbers, the critical energy $k_BT_c$, with $k_B$ the Boltzmann constant, is larger than the excited band widths and harmonic oscillator energy. Using conservation of total energy and atom number, we show that the temperature increases after the lattice transformation. Finally, we estimate the time scale for a two-body collision-aided decay of the condensate as a function of lattice parameters. The decay involves two processes, the dominant one in which both colliding atoms decay to the ground band, and the second involving excitation of one atom to a higher band. For this estimate, we have used TB wave functions for the lowest four bands, and numerical estimates for higher bands. The decay rate rapidly increases with lattice depth, but stays smaller than the tunneling rate between the $s$ and $p$ orbitals in adjacent wells. }, doi = {10.1103/PhysRevA.88.033615}, url = {http://arxiv.org/abs/1308.4449v1}, author = {Saurabh Paul and Eite Tiesinga} } @article {1284, title = {Feshbach Resonances in Ultracold Gases}, journal = {Reviews of Modern Physics}, volume = {82}, year = {2010}, month = {2010/4/29}, pages = {1225 - 1286}, abstract = { Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. They have found numerous experimental applications, opening up the way to important breakthroughs. This Review broadly covers the phenomenon of Feshbach resonances in ultracold gases and their main applications. This includes the theoretical background and models for the description of Feshbach resonances, the experimental methods to find and characterize the resonances, a discussion of the main properties of resonances in various atomic species and mixed atomic species systems, and an overview of key experiments with atomic Bose-Einstein condensates, degenerate Fermi gases, and ultracold molecules. }, doi = {10.1103/RevModPhys.82.1225}, url = {http://arxiv.org/abs/0812.1496v2}, author = {Cheng Chin and Rudolf Grimm and Paul Julienne and Eite Tiesinga} }