Detection of antiferromagnetic order by cooling atoms in an optical lattice*

We have realized the Fermi-Hubbard model with fermionic $^{6}$Li atoms in a three-dimensional compensated optical lattice. \footnote{R. A. Hart, P. M. Duarte et al., Nature 519, 211-214 (2015).} The compensated optical lattice has provided low enough temperatures to produce short-range antiferromagnetic (AF) spin correlations, which we detect via Bragg scattering of light. Previously, we reached temperatures down to 1.4 times that of the AFM phase transition, more than a factor of 2 below temperatures obtained previously in 3D optical lattices with fermions. In order to further reduce the entropy in the compensated lattice, we implement an entropy conduit - which is a single blue detuned laser beam with a waist size smaller than the overall atomic sample size. This repulsive narrow potential provides a conductive metallic path between the low entropy core and the edges of the atomic sample where atoms may be evaporated. In addition, the entropy conduit may store entropy, thus further lowering the entropy in the core. We will report on the status of these efforts to further cool atoms in the optical lattice.