title: Compressibility of a fermionic mott insulator of ultracold atoms.
abstract: We characterize the Mott insulating regime of a repulsively interacting Fermi gas of ultracold atoms in a three-dimensional optical lattice. We use in situ imaging to extract the central density of the gas and to determine its local compressibility. For intermediate to strong interactions, we observe the emergence of a plateau in the density as a function of atom number, and a reduction of the compressibility at a density of one atom per site, indicating the formation of a Mott insulator. Comparisons to state-of-the-art numerical simulations of the Hubbard model over a wide range of interactions reveal that the temperature of the gas is of the order of, or below, the tunneling energy scale. Our results hold great promise for the exploration of many-body phenomena with ultracold atoms, where the local compressibility can be a useful tool to detect signatures of different phases or phase boundaries at specific values of the filling.
authors.affiliation: Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005, USA.
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Duarte
authors.affiliation: Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005, USA.
authors.forename: Russell A
authors.initials: RA
authors.lastname: Hart
authors.affiliation: Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005, USA.
authors.forename: Tsung-Lin
authors.initials: TL
authors.lastname: Yang
authors.affiliation: Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005, USA.
authors.forename: Xinxing
authors.initials: X
authors.lastname: Liu
authors.affiliation: Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68.528, 21941-972 Rio de Janeiro, RJ, Brazil.
authors.forename: Thereza
authors.initials: T
authors.lastname: Paiva
authors.affiliation: Department of Physics and Astronomy, San Jose State University, San Jose, California 95192, USA.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Khatami
authors.affiliation: Department of Physics, University of California, Davis, California 95616, USA.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Scalettar
authors.affiliation: Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Nandini
authors.initials: N
authors.lastname: Trivedi
authors.affiliation: Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005, USA.
authors.forename: Randall G
authors.initials: RG
authors.lastname: Hulet