Metallic and Insulating Phases of Repulsively Interacting Fermions in a 3D Optical Lattice
U. Schneider,1
L. Hackermüller,1
S. Will,1
Th. Best,1
I. Bloch,1,2*
T. A. Costi,3
R. W. Helmes,4
D. Rasch,4
A. Rosch4
The fermionic Hubbard model plays a fundamental role in the
description of strongly correlated materials. We have realized
this Hamiltonian in a repulsively interacting spin mixture of
ultracold
40K atoms in a three-dimensional (3D) optical lattice.
Using in situ imaging and independent control of external confinement
and lattice depth, we were able to directly measure the compressibility
of the quantum gas in the trap. Together with a comparison to
ab initio dynamical mean field theory calculations, we show
how the system evolves for increasing confinement from a compressible
dilute metal over a strongly interacting Fermi liquid into a
band-insulating state. For strong interactions, we find evidence
for an emergent incompressible Mott insulating phase. This demonstrates
the potential to model interacting condensed-matter systems
using ultracold fermionic atoms.
2 Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
3 Institut für Festkörperforschung and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany.
4 Institut für Theoretische Physik, Universität zu Köln, 50937 Cologne, Germany.
* To whom correspondence should be addressed. E-mail: bloch{at}uni-mainz.de
