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Scattering Length (scattering + length)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

X-ray investigation of CdSe nanowires

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2009
Özgül Kurtulu
Abstract CdSe nanowires (NWs) have been prepared by a solution,liquid,solid (SLS) approach using Bi nanocatalysts. Structural characterization has been performed by X-ray powder diffraction providing an admixture of wurtzite and zinc-blende (ZB) structure units separated by different types of stacking faults. The relative contributions of ZB type stacking units within the NWs were determined to be in the order of 3,6% from a set of ratios of reflection intensities appearing in only wurtzite structure to those appearing in both ZB and wurtzite (W) structure. In addition, the anisotropy of domain size within the NWs was evaluated from the evolution of peak broadening for increasing scattering length. The coherence lengths along the growth direction are found to be changing between 16 and 21,nm, smaller than the results obtained from TEM measurement, while the NW diameters are determined to be between 5 and 8,nm which is in good agreement with TEM inspection. [source]

A neutron interferometric measurement of a phase shift induced by Laue transmission

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2010
J. Springer
The phenomenon of a neutron phase shift due to Laue transmission in a perfect crystal blade is discussed. Quantitative measurements of this phase shift are presented in the vicinity of the Bragg condition well in agreement with numerical calculations. The phase shift shows a strong angular sensitivity and might constitute an interesting opportunity for precision measurements of fundamental quantities like the neutron,electron scattering length or gravitational short-range interactions. [source]

Speed of sound in an optical lattice

ANNALEN DER PHYSIK, Issue 10 2010
Z. Koinov
Abstract A system of equal mixture of 6Li atomic Fermi gas of two hyperfine states loaded into a cubic three-dimensional optical lattice is studied assuming a negative scattering length (BCS side of the Feshbach resonance). When the interaction is attractive, fermionic atoms can pair and form a superfluid. The dispersion of the phonon-like mode and the speed of sound in the long-wavelength limit are obtained by solving the Bethe-Salpeter equations for the collective modes of the attractive Hubbard Hamiltonian. [source]

Functional renormalization group approach to the BCS-BEC crossover

ANNALEN DER PHYSIK, Issue 9 2010
S. Diehl
Abstract The phase transition to superfluidity and the BCS-BEC crossover for an ultracold gas of fermionic atoms is discussed within a functional renormalization group approach. Non-perturbative flow equations, based on an exact renormalization group equation, describe the scale dependence of the flowing or average action. They interpolate continuously from the microphysics at atomic or molecular distance scales to the macroscopic physics at much larger length scales, as given by the interparticle distance, the correlation length, or the size of the experimental probe. We discuss the phase diagram as a function of the scattering length and the temperature and compute the gap, the correlation length and the scattering length for molecules. Close to the critical temperature, we find the expected universal behavior. Our approach allows for a description of the few-body physics (scattering and molecular binding) and the many-body physics within the same formalism. [source]

Quantum phase diagram for homogeneous Bose-Einstein condensate

ANNALEN DER PHYSIK, Issue 4 2005
H. Kleinert
Abstract We calculate the quantum phase transition for a homogeneous Bose gas in the plane of s -wave scattering length as and temperature T. This is done by improving a one-loop result near the interaction-free Bose-Einstein critical temperature Tc(0) with the help of recent high-loop results on the shift of the critical temperature due to a weak atomic repulsion based on variational perturbation theory. The quantum phase diagram shows a nose above Tc(0), so that we predict the existence of a reentrant transition above Tc(0), where an increasing repulsion leads to the formation of a condensate. [source]