44 research outputs found
Bichromatic Imaging of Single Molecules in an Optical Tweezer Array
We report on a novel bichromatic fluorescent imaging scheme for
background-free detection of single CaF molecules trapped in an optical tweezer
array. By collecting fluorescence on one optical transition while using another
for laser-cooling, we achieve an imaging fidelity of 97.7(2)% and a
non-destructive detection fidelity of 95.5(6)%. We characterize loss mechanisms
of our scheme, many of which are generically relevant to the fluorescent
detection of trapped molecules, including two-photon decay and admixtures of
higher excited states that are induced by the trapping light
Evolution of Fermion Pairing from Three to Two Dimensions
We follow the evolution of fermion pairing in the dimensional crossover from
3D to 2D as a strongly interacting Fermi gas of Li atoms becomes confined
to a stack of two-dimensional layers formed by a one-dimensional optical
lattice. Decreasing the dimensionality leads to the opening of a gap in
radio-frequency spectra, even on the BCS-side of a Feshbach resonance. The
measured binding energy of fermion pairs closely follows the theoretical
two-body binding energy and, in the 2D limit, the zero-temperature mean-field
BEC-BCS theory.Comment: 5 pages, 4 figure
Motion of a Solitonic Vortex in the BEC-BCS Crossover
We observe a long-lived solitary wave in a superfluid Fermi gas of Li
atoms after phase-imprinting. Tomographic imaging reveals the excitation to be
a solitonic vortex, oriented transverse to the long axis of the cigar-shaped
atom cloud. The precessional motion of the vortex is directly observed, and its
period is measured as a function of the chemical potential in the BEC-BCS
crossover. The long period and the correspondingly large ratio of the inertial
to the bare mass of the vortex are in good agreement with estimates based on
superfluid hydrodynamics that we derive here using the known equation of state
in the BEC-BCS crossover
-Enhanced Imaging of Molecules in an Optical Trap
We report non-destructive imaging of optically trapped calcium monofluoride
(CaF) molecules using in-situ -enhanced gray molasses cooling.
times more fluorescence is obtained compared to destructive on-resonance
imaging, and the trapped molecules remain at a temperature of
. The achieved number of scattered photons makes possible
non-destructive single-shot detection of single molecules with high fidelity.Comment: 6 pages, 4 figure
Spin-Injection Spectroscopy of a Spin-Orbit Coupled Fermi Gas
The coupling of the spin of electrons to their motional state lies at the
heart of recently discovered topological phases of matter. Here we create and
detect spin-orbit coupling in an atomic Fermi gas, a highly controllable form
of quantum degenerate matter. We reveal the spin-orbit gap via spin-injection
spectroscopy, which characterizes the energy-momentum dispersion and spin
composition of the quantum states. For energies within the spin-orbit gap, the
system acts as a spin diode. To fully inhibit transport, we open an additional
spin gap, thereby creating a spin-orbit coupled lattice whose spinful band
structure we probe. In the presence of s-wave interactions, such systems should
display induced p-wave pairing, topological superfluidity, and Majorana edge
states
An Optical Tweezer Array of Ultracold Molecules
Arrays of single ultracold molecules promise to be a powerful platform for
many applications ranging from quantum simulation to precision measurement.
Here we report on the creation of an optical tweezer array of single ultracold
CaF molecules. By utilizing light-induced collisions during the laser cooling
process, we trap single molecules. The high densities attained inside the
tweezer traps have also enabled us to observe in the absence of light
molecule-molecule collisions of laser cooled molecules for the first time
Spin Transport in a Mott Insulator of Ultracold Fermions
Strongly correlated materials are expected to feature unconventional
transport properties, such that charge, spin, and heat conduction are
potentially independent probes of the dynamics. In contrast to charge
transport, the measurement of spin transport in such materials is highly
challenging. We observed spin conduction and diffusion in a system of ultracold
fermionic atoms that realizes the half-filled Fermi-Hubbard model. For strong
interactions, spin diffusion is driven by super-exchange and
doublon-hole-assisted tunneling, and strongly violates the quantum limit of
charge diffusion. The technique developed in this work can be extended to
finite doping, which can shed light on the complex interplay between spin and
charge in the Hubbard model.Comment: 16 pages, 10 figure