The physics of high temperature superconductors is not well understood, although it is
known that the undoped parent compounds of many of them are antiferromagnetic (AF)
insulators. The Fermi-Hubbard model at half filling (one atom per lattice site) is known to
exhibit a phase transition to an antiferromagnetic insulator at a low temperature. We realize
the Fermi-Hubbard model by loading ultracold 6 Li atoms into a three-dimensional red-
detuned optical lattice. We have compensated the confining potential of the lattice with blue …

The Hubbard model contains only the essential ingredients to describe the behavior of
strongly interacting electrons moving in a periodic lattice. It describes particles that can
tunnel between sites in the lattice and that acquire an on-site interaction energy when two of
them occupy the same lattice site. This simple model is a prominent example of how strongly
correlated phases emerge from simple Hamiltonians. It gives rise to a Mott-metal insulator
transition, and at a density of one particle per site shows an antiferromagnetic ground state …