RESEARCH

We have Li 7 (bosons) in an optical lattice and our research is in the field of Quantum Simulation. We are interested in studying phenomena in Quantum Magentism: the ordered phases which arise when the dominant interaction between partiles on a lattice is superexchange. In particular, the 2-component Bose Hubbard Hamiltonian can be directly mapped onto the Heisenberg spin Hamilitonan. In the context of the Bose Hubbard model, superexchange is a second order tunneling process, characterized by a matrix element "t^2/U." Here "t" is the hopping and "U" is the on-site interaction. The phase diagram of this Hamiltonian includes feromagnetic and anti-ferromagnetic phases aligned either with the quantization axis "z" or with a line in the the "xy"-plane. The main limitations so far for observing the full phase diagram of this model have been the slo rate of the superexchange process compared to the lifetimes of cold atoms in optical lattices and the very low critical temperatures required for superexchange to be the dominant interactions. Li 7 promises to make improvents on both fronts. Its light mass leads to faster tunneling, compared to other atoms, such as Rb, commonly used in Quantum Simulation experiments, so "t^2/U" is large. In addition, the critical temperature for magnetic ordering is also on the order of "t^/U," so it can be reached more easily with Li.

LITHIUM-7 BEC

As of Dec 24, 2013 we have a Li-7 BEC. Here is an absorption image of the BEC surrounded by a thermal cloud.