12,729 research outputs found
Observation of two-orbital spin-exchange interactions with ultracold SU(N)-symmetric fermions
We report on the direct observation of spin-exchanging interactions in a
two-orbital SU(N)-symmetric quantum gas of ytterbium in an optical lattice. The
two orbital states are represented by two different (meta-)stable electronic
configurations of fermionic Yb-173. A strong spin-exchange between particles in
the two separate orbitals is mediated by the contact interaction between atoms,
which we characterize by clock shift spectroscopy in a 3D optical lattice. We
find the system to be SU(N)-symmetric within our measurement precision and
characterize all relevant scattering channels for atom pairs in combinations of
the ground and the excited state. Elastic scattering between the orbitals is
dominated by the antisymmetric channel, which leads to the strong spin-exchange
coupling. The exchange process is directly observed, by characterizing the
dynamic equilibration of spin imbalances between two large ensembles in the two
orbital states, as well as indirectly in atom pairs via interaction shift
spectroscopy in a 3D lattice. The realization of a stable SU(N)-symmetric
two-orbital Hubbard Hamiltonian opens the route towards experimental quantum
simulation of condensed-matter models based on orbital interactions, such as
the Kondo lattice model.Comment: Correction: In the original version of this preprint the assignment
of states with symmetric electronic wavefunction (|eg+>) and with
antisymmetric electronic wavefunction (|eg->) to the observed spectral lines
was inverted. This has been corrected in the current version. The results of
the paper remain unchanged, with the exchange coupling being inverted to a
ferromagnetic exchang
Observation of dynamical instability for a Bose-Einstein condensate in a moving 1D optical lattice
We have experimentally studied the unstable dynamics of a harmonically
trapped Bose-Einstein condensate loaded into a 1D moving optical lattice. The
lifetime of the condensate in such a potential exhibits a dramatic dependence
on the quasimomentum state. This is unambiguously attributed to the onset of
dynamical instability, after a comparison with the predictions of the
Gross-Pitaevskii theory. Deeply in the unstable region we observe the rapid
appearance of complex structures in the atomic density profile, as a
consequence of the condensate phase uniformity breakdown
Bloch oscillations in Fermi gases
The possibility of Bloch oscillations for a degenerate and superfluid Fermi
gas of atoms in an optical lattice is considered. For a one-component
degenerate gas the oscillations are suppressed for high temperatures and band
fillings. For a two-component gas the Landau criterion is used for specifying
the regime where Bloch oscillations of the superfluid may be observed. We show
how the amplitude of Bloch oscillations varies along the BCS-BEC crossover.Comment: 4 pages, 2 figures. explanations adde
Investigations on the binding of mercury ions to albumins employing differential pulse voltammetry.
The binding of zinc (II) to a double-stranded oligodeoxyribonucleotide; a voltammetric study.
Binding of zinc to a 19 mer double-stranded oligodeoxyribonucleotide was investigated by anodic stripping voltammetry and cyclic voltammetry in order to understand the roles of zinc in DNA cleavage catalyzed by mung bean nuclease. These methods rely on the direct monitoring of zinc oxidation current in the absence and in the presence of the oligo. Zinc titration curves with the ds-oligodeoxyribonucleotide were obtained in concentrations ranging from 3.62Ă—10-9 to 3.62Ă—10-8 M and 4.06Ă—10-10 to 5.25Ă—10-9 M. The acquired data were used to determine the dissociation constant, stoichiometry and zinc binding sites of the complex and to understand the specific changes of ds-oligodeoxyribonucleotide secondary structure by zinc binding. The oxidation-reduction process of zinc was also investigated by cyclic voltammetry through I (oxidation current) versus v1/2 (square root of scan rate) curves in the absence and in the presence of the double-stranded oligodeoxyribonucleotide
Identification and characterization of a novel cassava (Manihot esculenta Crantz) clone with high free sugar content and novel starch.
Wannier-Stark ladders in one-dimensional elastic systems
The optical analogues of Bloch oscillations and their associated
Wannier-Stark ladders have been recently analyzed. In this paper we propose an
elastic realization of these ladders, employing for this purpose the torsional
vibrations of specially designed one-dimensional elastic systems. We have
measured, for the first time, the ladder wave amplitudes, which are not
directly accessible either in the quantum mechanical or optical cases. The wave
amplitudes are spatially localized and coincide rather well with theoretically
predicted amplitudes. The rods we analyze can be used to localize different
frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let
Unstable and stable regimes of polariton condensation
Modulational instabilities play a key role in a wide range of nonlinear
optical phenomena, leading e.g. to the formation of spatial and temporal
solitons, rogue waves and chaotic dynamics. Here we experimentally demonstrate
the existence of a modulational instability in condensates of cavity
polaritons, arising from the strong coupling of cavity photons with quantum
well excitons. For this purpose we investigate the spatiotemporal coherence
properties of polariton condensates in GaAs-based microcavities under
continuous-wave pumping. The chaotic behavior of the instability results in a
strongly reduced spatial and temporal coherence and a significantly
inhomogeneous density. Additionally we show how the instability can be tamed by
introducing a periodic potential so that condensation occurs into negative mass
states, leading to largely improved coherence and homogeneity. These results
pave the way to the exploration of long-range order in dissipative quantum
fluids of light within a controlled platform.Comment: 7 pages, 5 figure
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