Pedro Duarte Feb 28 Abstract

Characterizing the antiferromagnetic ordering of fermions in an optical lattice realization of the Fermi-Hubbard model

The Fermi-Hubbard model is the simplest possible model containing the necessary ingredients to describe the behavior of strongly correlated materials. This model considers particles that can hop between sites in a lattice and that acquire an interaction energy when two of them occupy the same lattice site. We realize the Fermi-Hubbard model with fermionic 6Li atoms in a three-dimensional, red-detuned optical lattice, formed at the intersection of three retro-reflected laser beams. The lattice is compensated by the addition of three blue-detuned beams which overlap each of the lattice laser beams, but are not retro-reflected. Using the compensated lattice potential, we have reached temperatures low enough to produce antiferromagnetic (AF) spin correlations, which we detect via Bragg scattering of light off of the atoms. The variation of the measured AF correlations as a function of the on-site interaction strength, U=t, provides a way to determine the temperature of the atoms in the lattice by comparison with results from Quantum Monte-Carlo calculations. In this talk I present our measurement of the spin structure factor via Bragg scattering, along with studies of the effect of the compensating potential for cooling the atoms in the lattice and also enlarging the extent of the AF phase in the system.