Search results for "Number"
showing 10 items of 3939 documents
Method of quantitative analysis of filler dispersion in composite systems with spherical inclusions
2011
In this work, a quantitative analysis method for the estimation of filler dispersion degree of filler particles in composite systems is presented and described. According to the procedure offered dispersion of filler particles of any form is associated with their area and the dispersion parameter D is defined as the probability to fall in a certain range of the particle area distribution. The method has been applied to both model and real systems characterized by different dispersion levels and various filler content. Final results highlight that for the case of better filler dispersion, the characteristic parameter, D, increases, since the quantity of filler particles having identical area…
Properties of the Phonon Gas in Ultrathin Membranes at Low Temperature
1998
We analyze heat conduction by phonons in ultrathin membranes by constructing a new theoreticalframework which implies a crossover from a bulk three-dimensional phonon distribution into a quasi-two-dimensional distribution when the temperature is lowered. We calculate the corresponding changesin the relevant thermodynamic quantities. At the end we make a comparison to experimental data.[S0031-9007(98)07273-1]
Algebraic value of the electrooptic coefficients and nature of charge carriers in batio3single crystals
1989
Abstract Some monodomain pure and Fe doped barium titanate monocrystals are studied. The algebraic values of the electrooptic coefficients r 13 and r 33 are evaluated using an interferometric method. Then, from energy transfer results it is possible to conclude that majority carriers are positive charges in all the samples.
Resonances over a potential well in an island
2020
In this paper we study the distribution of scattering resonances for a multidimensional semi-classical Schr\"odinger operator, associated to a potential well in an island at energies close to the maximal one that limits the separation of the well and the surrounding sea.
Trapping of laser-vaporized alkali metal atoms in rare-gas matrices
1999
Abstract Alkali metal atoms prepared by laser ablation of solid Li and Na are trapped in Ar, Kr, and Xe matrices and studied by electron paramagnetic resonance spectroscopy (EPR) at 15 K. Evidence for tight trapping sites, not observed for atoms generated by conventional Knudsen oven techniques, is presented. The novel tight trapping sites are characterized by a large increase in the isotropic hyperfine coupling constant and a simultaneous decrease in the isotropic g -value. Based on the EPR data, it is suggested that the observed tight trapping corresponds to single substitution of lattice atoms in Ar, Kr, and Xe matrices.
Vortices in rotating two-component boson and fermion traps
2010
Quantum liquids may carry angular momentum by the formation of vortex states. This is well known for Bose-Einstein condensates in rotating traps, and was even found to occur in quantum dots at strong magnetic fields. Here we consider a two-component quantum liquid, where coreless vortices and interlaced lattices of coreless vortices appear in a very similar way for fermions and bosons with repulsive two-body interactions. The ground states at given angular momentum, as well as the pair correlations for equal and different numbers of atoms in the two components, are studied. (C) 2009 Elsevier B.V. All rights reserved.
Probing number squeezing of ultracold atoms across the superfluid-Mott insulator transition.
2005
The evolution of on-site number fluctuations of ultracold atoms in optical lattices is experimentally investigated by monitoring the suppression of spin-changing collisions across the superfluid-Mott insulator transition. For low atom numbers, corresponding to an average filling factor close to unity, large on-site number fluctuations are necessary for spin-changing collisions to occur. The continuous suppression of spin-changing collisions is thus a direct evidence for the emergence of number-squeezed states. In the Mott insulator regime, we find that spin-changing collisions are suppressed until a threshold atom number, consistent with the number where a Mott plateau with doubly-occupied …
Persistent currents in a circular array of Bose-Einstein condensates
2002
A ring-shaped array of Bose-Einstein condensed atomic gases can display circular currents if the relative phase of neighboring condensates becomes locked to certain values. It is shown that, irrespective of the mechanism responsible for generating these states, only a restricted set of currents are stable, depending on the number of condensates, on the interaction and tunneling energies, and on the total number of particles. Different instabilities due to quasiparticle excitations are characterized and possible experimental setups for testing the stability prediction are also discussed.
Strong enhancement of Penning ionization for asymmetric atom pairs in cold Rydberg gases: the Tom and Jerry effect
2016
We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole–dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d , n i , of both atoms. While for symmetric atom pairs with the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive—for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d depende…
Exploring helical phases of matter in bosonic ladders
2020
Ladder models of ultracold atoms offer a versatile platform for the experimental and theoretical study of different phenomena and phases of matter linked to the interplay between artificial gauge fields and interactions. Strongly correlated helical states are known to appear for specific ratios of the particle and magnetic flux densities and they can often be interpreted as a one-dimensional limit of fractional quantum Hall states, thus being called pretopological. Their signatures, however, are typically hard to observe due to the small gaps characterizing these states. Here we investigate bosonic ladder models at filling factor 1. Based on bosonization, renormalization group and matrix pr…