9 research outputs found
Localized magnetic moments with tunable spin exchange in a gas of ultracold fermions
We report on the experimental realization of a state-dependent lattice for a
two-orbital fermionic quantum gas with strong interorbital spin exchange. In
our state-dependent lattice, the ground and metastable excited electronic
states of Yb take the roles of itinerant and localized magnetic
moments, respectively. Repulsive on-site interactions in conjunction with the
tunnel mobility lead to spin exchange between mobile and localized particles,
modeling the coupling term in the well-known Kondo Hamiltonian. In addition, we
find that this exchange process can be tuned resonantly by varying the on-site
confinement. We attribute this to a resonant coupling to center-of-mass excited
bound states of one interorbital scattering channel
Direct probing of the Mott crossover in the SU() Fermi-Hubbard model
The Fermi-Hubbard model (FHM) is a cornerstone of modern condensed matter
theory. Developed for interacting electrons in solids, which typically exhibit
SU() symmetry, it describes a wide range of phenomena, such as metal to
insulator transitions and magnetic order. Its generalized SU()-symmetric
form, originally applied to multi-orbital materials such as transition-metal
oxides, has recently attracted much interest owing to the availability of
ultracold SU()-symmetric atomic gases. Here we report on a detailed
experimental investigation of the SU()-symmetric FHM using local probing of
an atomic gas of ytterbium in an optical lattice to determine the equation of
state through different interaction regimes. We prepare a low-temperature
SU()-symmetric Mott insulator and characterize the Mott crossover,
representing important steps towards probing predicted novel SU()-magnetic
phases
Observation of coherent multiorbital polarons in a two-dimensional Fermi gas
We report on the experimental observation of multiorbital polarons in a
two-dimensional Fermi gas of atoms formed by mobile
impurities in the metastable orbital and a Fermi sea in the
ground-state orbital. We spectroscopically probe the energies
of attractive and repulsive polarons close to an orbital Feshbach resonance and
characterize their coherence by measuring the quasiparticle residue. For all
probed interaction parameters, the repulsive polaron is a long-lived
quasiparticle with a decay rate more than 2 orders of magnitude below its
energy. We formulate a many-body theory, which accurately treats the
interorbital interactions in two dimensions and agrees well with the
experimental results. Our work paves the way for the investigation of many-body
physics in multiorbital ultracold Fermi gases.Comment: 6 pages, 4 figures; Supplementary Materia