1,530 research outputs found
Two-color photoassociation spectroscopy of ytterbium atoms and the precise determinations of s-wave scattering lengths
By performing high-resolution two-color photoassociation spectroscopy, we
have successfully determined the binding energies of several of the last bound
states of the homonuclear dimers of six different isotopes of ytterbium. These
spectroscopic data are in excellent agreement with theoretical calculations
based on a simple model potential, which very precisely predicts the s-wave
scattering lengths of all 28 pairs of the seven stable isotopes. The s-wave
scattering lengths for collision of two atoms of the same isotopic species are
13.33(18) nm for ^{168}Yb, 3.38(11) nm for ^{170}Yb, -0.15(19) nm for ^{171}Yb,
-31.7(3.4) nm for ^{172}Yb, 10.55(11) nm for ^{173}Yb, 5.55(8) nm for ^{174}Yb,
and -1.28(23) nm for ^{176}Yb. The coefficient of the lead term of the
long-range van der Waals potential of the Yb_2 molecule is C_6=1932(30) atomic
units J nm^6).Comment: 9 pages, 7 figure
Evidence for unconventional superconducting fluctuations in heavy-fermion compound CeNi2Ge2
We present evidence for unconventional superconducting fluctuations in a
heavy-fermion compound CeNiGe. The temperature dependence of the
Ge nuclear-spin-lattice-relaxation rate indicates the
development of magnetic correlations and the formation of a Fermi-liquid state
at temperatures lower than K, where is constant. The
resistance and measured on an as-grown sample decrease below K and K, respectively; these
are indicative of the onset of superconductivity. However, after annealing the
sample to improve its quality, these superconducting signatures disappear.
These results are consistent with the emergence of unconventional
superconducting fluctuations in close proximity to a quantum critical point
from the superconducting to the normal phase in CeNiGe.Comment: 4pages,5figures,to appear in J. Phys. Soc. Jp
Rhythmic expression of Nocturnin mRNA in multiple tissues of the mouse
BACKGROUND: Nocturnin was originally identified by differential display as a circadian clock regulated gene with high expression at night in photoreceptors of the African clawed frog, Xenopus laevis. Although encoding a novel protein, the nocturnin cDNA had strong sequence similarity with a C-terminal domain of the yeast transcription factor CCR4, and with mouse and human ESTs. Since its original identification others have cloned mouse and human homologues of nocturnin/CCR4, and we have cloned a full-length cDNA from mouse retina, along with partial cDNAs from human, cow and chicken. The goal of this study was to determine the temporal pattern of nocturnin mRNA expression in multiple tissues of the mouse. RESULTS: cDNA sequence analysis revealed a high degree of conservation among vertebrate nocturnin/CCR4 homologues along with a possible homologue in Drosophila. Northern analysis of mRNA in C3H/He and C57/Bl6 mice revealed that the mNoc gene is expressed in a broad range of tissues, with greatest abundance in liver, kidney and testis. mNoc is also expressed in multiple brain regions including suprachiasmatic nucleus and pineal gland. Furthermore, mNoc exhibits circadian rhythmicity of mRNA abundance with peak levels at the time of light offset in the retina, spleen, heart, kidney and liver. CONCLUSION: The widespread expression and rhythmicity of mNoc mRNA parallels the widespread expression of other circadian clock genes in mammalian tissues, and suggests that nocturnin plays an important role in clock function or as a circadian clock effector
Simulation of the many-body dynamical quantum Hall effect in an optical lattice
We propose an experimental scheme to simulate the many-body dynamical quantum
Hall effect with ultra-cold bosonic atoms in a one-dimensional optical lattice.
We first show that the required model Hamiltonian of a spin-1/2 Heisenberg
chain with an effective magnetic field and tunable parameters can be realized
in this system. For dynamical response to ramping the external fields, the
quantized plateaus emerge in the Berry curvature of the interacting atomic spin
chain as a function of the effective spin-exchange interaction. The
quantization of this response in the parameter space with the
interaction-induced topological transition characterizes the many-body
dynamical quantum Hall effect. Furthermore, we demonstrate that this phenomenon
can be observed in practical cold-atom experiments with numerical simulations.Comment: 8 pages, 3 figures; accepted in Quantum Information Processin
Microscopic observation of magnon bound states and their dynamics
More than eighty years ago, H. Bethe pointed out the existence of bound
states of elementary spin waves in one-dimensional quantum magnets. To date,
identifying signatures of such magnon bound states has remained a subject of
intense theoretical research while their detection has proved challenging for
experiments. Ultracold atoms offer an ideal setting to reveal such bound states
by tracking the spin dynamics after a local quantum quench with single-spin and
single-site resolution. Here we report on the direct observation of two-magnon
bound states using in-situ correlation measurements in a one-dimensional
Heisenberg spin chain realized with ultracold bosonic atoms in an optical
lattice. We observe the quantum walk of free and bound magnon states through
time-resolved measurements of the two spin impurities. The increased effective
mass of the compound magnon state results in slower spin dynamics as compared
to single magnon excitations. In our measurements, we also determine the decay
time of bound magnons, which is most likely limited by scattering on thermal
fluctuations in the system. Our results open a new pathway for studying
fundamental properties of quantum magnets and, more generally, properties of
interacting impurities in quantum many-body systems.Comment: 8 pages, 7 figure
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