Heavy fermions in an optical lattice

We employ a mean-field theory to study ground-state properties and transport of a two-dimensional gas of ultracold alkaline-earth-metal atoms governed by the Kondo lattice Hamiltonian plus a parabolic confining potential. In a homogenous system, this mean-field theory is believed to give a qualitatively correct description of heavy-fermion metals and Kondo insulators: It reproduces the Kondo-like scaling of the quasiparticle mass in the former and the same scaling of the excitation gap in the latter. In order to understand ground-state properties in a trap, we extend this mean-field theory via local-density approximation. We find that the Kondo insulator gap manifests as a shell structure in the trapped density profile. In addition, a strong signature of the large Fermi surface expected for heavy-fermion systems survives the confinement and could be probed in time-of-flight experiments. From a full self-consistent diagonalization of the mean-field theory, we are able to study dynamics in the trap. We find that the mass enhancement of quasiparticle excitations in the heavy-Fermi liquid phase manifests as slowing of the dipole oscillations that result from a sudden displacement of the trap center.