Probing and Preparing Novel States of Quantum Gases in Optical Lattices

Quantum degenerate gases placed in optical lattices is an attractive platform to explore systems analogous to condensed matter and deepen our understanding of many-body physics by taking advantage of the tools and precision of atomic physics. First I will discuss our application of Bragg scattering as originally realized in x-ray and neutron scattering to study ultracold rubidium atoms confined in a three-dimensional optical lattice. This allowed us to study the atomic wavefunctions in the quantum regime, as well as to probe the superfluid-to-Mott insulator quantum phase transition. Next, I will describe a new scheme to create artificial magnetic fields for charge neutral ultracold atoms in optical lattices using two-photon, laser-assisted tunneling. This realizes the Harper Hamiltonian, a lattice model for charged particles in magnetic fields whose band structure is the fractal Hofstadter butterfly. This system is experimentally studied by observing the in-situ expansion of rubidium atoms in a two-dimensional optical lattice.