In this project, the optical version of kagome lattice was realized for the first time by trapping rubidium-87 atoms in a bichromatic superlattice. The kagome optical lattice is expected to pave the way for characterizing and manipulating a new frustrated quantum material with ultracold atoms. The team examined phase transitions in a structure-dependent superfluid-Mott by employing the tunable triangular–kago me geometry. In parallel, the team investigated the magnetic properties of the spinor Bose gas by employing spin-sensitive spin-echo imaging with high optical resolution.

Reference

[1] C.K. Thomas, T.H. Barter, T. Leung, M. Okano, G.-B. Jo, J. Guzman, I. Kimchi, A. Vishwanath, D.M. Stamper-Kurn Mean-field scaling of the superfluid to Mott insulator transition in a 2D optical superlattice Physical Review Letters 119, 100402 (2017)

[2] Gyu-Boong Jo, Jennie Guzman, Claire K. Thomas, Pavan Hosur, Ashvin Viswanath, and Dan M. Stamper-Kurn .Ultracold Atoms in a Tunable Optical Kagome Lattice Physical Review Letters 108 045305 (2012)

The mean-field treatment of the Bose-Hubbard model predicts properties of lattice-trapped gases to be insensitive to the specific lattice geometry once system energies are scaled by the lattice coordination number z. We test this scaling directly by comparing coherence properties of 87Rb gases that are driven across the superfluid to Mott insulator transition within optical lattices of either the kagome (z 1⁄4 4) or the triangular (z 1⁄4 6) geometries. The coherent fraction measured for atoms in the kagome lattice is lower than for those in a triangular lattice with the same interaction and tunneling energies. A comparison of measurements from both lattices agrees quantitatively with the scaling prediction.

Reference

[1] C.K. Thomas, T.H. Barter, T. Leung, M. Okano, G.-B. Jo, J. Guzman, I. Kimchi, A. Vishwanath, D.M. Stamper-Kurn Mean-field scaling of the superfluid to Mott insulator transition in a 2D optical superlattice Physical Review Letters 119, 100402 (2017)

[2] Gyu-Boong Jo, Jennie Guzman, Claire K. Thomas, Pavan Hosur, Ashvin Viswanath, and Dan M. Stamper-Kurn .Ultracold Atoms in a Tunable Optical Kagome Lattice Physical Review Letters 108 045305 (2012)

We investigate the long-term dynamics of spin textures prepared by cooling unmagnetized spinor gases of F=1 87Rb to quantum degeneracy, observing domain coarsening and a strong dependence of the equilibration dynamics on the quadratic Zeeman shift q. For small values of |q|, the textures arrive at a configuration independent of the initial spin-state composition, characterized by large length-scale spin domains and the establishment of easy-axis (negative q) or easy-plane (positive q) magnetic anisotropy. For larger |q|, equilibration is delayed as the spin-state composition of the degenerate spinor gas remains close to its initial value. These observations support the mean-field equilibrium phase diagram predicted for a ferromagnetic spinor Bose-Einstein condensate and also illustrate that equilibration is achieved under a narrow range of experimental settings, making the F=1 87Rb gas more suitable for studies of nonequilibrium quantum dynamics.

Reference

[1] J.Guzman, G.-B.Jo, A.N. Wenz, K.W. Murch, C.K. Thomas, D.M. Stamper-Kurn Long Time scale dynamics in a degenerate F=1 Rb spinor condensate Physical Review A 84 063625 (2011

In this project, we addressed how many- body phenomena can enhance the quantum coherence of Bose-Einstein condensates in a double-well Josephson junction realized in an micro-fabricated atom chip. One example is a non-classical number-squeezed state of BECs induced from mean-field interaction effects, confirmed by matter-wave interferometry. This seminal work has been regarded as a proof of principle experiment for confined matter-wave interferometry with phase coherence times up to 200ms. With a controllable Josephson junction filled with bosonic superfluid, it was also demonstrated the generation of dark solitons by merging two condensates leads to phase-sensitive dissipation.

Reference

[1] G.-B. Jo et al., Matter-Wave Interferometry with Phase Fluctuating Bose-Einstein Condensates Physical Review Letters 99, 240406 (2007)

[2] G.-B. Jo et al., Phase Sensitive Recombination of Two Bose-Einstein Condensates on an Atom Chip Physical Review Letters 98, 180401 (2007)

[3] G.-B. Jo, et al., Phase Coherence Time and Number Squeezing of two Bose-Einstein Condensates on an Atom Chip Physical Review Letters 98, 030407 (2007)

Ultracold sodium atoms have been trapped inside a hollow-core optical fiber. The atoms are transferred from a free-space optical dipole trap into a trap formed by a red-detuned Gaussian light mode confined to the core of the fiber. We show that at least 5% of the atoms held initially in the free-space trap can be loaded into the core of the fiber and retrieved outside. Trapped atoms in a fiver can serve as a confined atom interferometer, which can tremendously enhance the interrogation time. Furthermore, the high-density atomic ensemble allows for us to explore non-linear quantum optics in the presence of strong coupling between atoms and photons inside the finer

Reference

[1] C.A. Christensen, S. Will, M. Saba, G.-B. Jo, Y.Shin, W. Ketterle, and D.E. Pritchard Trapping of Ultracold Atoms in a Hollow-core Photonic Crystal Fiber Physical Review A 78 033429 (2008)

A Fermi gas with repulsive short range interactions is regarded as the primary example of the Fermi liquid. Nevertherless, repulsively interacting Fermi gases of cold atoms have draw less attention due to the experimental challenges and has remained less explored until recent years. In this work, we demonstrate an unexpected new route to studies of repulsive Fermi gases by parting from conventional experimental methods. For example, the sudden quench of strong interactions is achieved by changing magnetic field near the Feshbach resonance of Litium-6 fermions, setting the stage for the study of a repulsively interacting Fermi gas. This work addresses a possible quantum magnetism in ultracold atoms shedding lights on the strongly correlated physics. This work has triggered enormous theoretical interest revealing new aspects of a repulsive fermions.

Reference

Gyu-Boong Jo, Ye-Ryuoung Lee, Jae-Hoon Choi, Caleb A. Christensen, Tony H. Kim, Joseph H.Thywissen, David E. Pritchard and Wolfgang Ketterle Itinerant Ferromagnetism in a Fermi Gas of Ultracold atoms Science 325 1521-1524 (2009)