Heavy fermions in an optical lattice

TL;DR

This paper uses mean-field theory to explore the properties of heavy fermions in an ultracold atomic gas within an optical lattice, revealing shell structures and Fermi surface signatures that mimic heavy fermion metals.

Contribution

It extends mean-field theory with local-density approximation to analyze trapped systems and predicts observable signatures of heavy fermion behavior in cold atom experiments.

Findings

Kondo insulator gap appears as shell structure in density profiles

Large Fermi surface signatures persist under confinement

Mass enhancement slows dipole oscillations in the heavy Fermi liquid phase

Abstract

We employ a mean-field theory to study ground-state properties and transport of a two-dimensional gas of ultracold alklaline-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.