We examine a scheme for the optical creation of a superfluid vortex in a trapped Bose-Einstein condensate, using the stimulated Raman adiabatic passage technique (STIRAP). By exposing an oblate, ...axis-symmetric condensate to two copropagating laser pulses, one can transfer external angular momentum from the light field to the matter wave, if one of the beams is the fundamental Gaussian mode and the other is a Gauss-Laguerre mode of angular momentum 1({Dirac_h}/2{pi}). We demonstrate the complete transfer efficiency by numerical integration of the multicomponent Gross-Pitaevskii equation and explain the results with an intuitive and accurate approximation within the Thomas-Fermi limit. In addition, we discuss residual excitations (breathing modes) which occur in the two-dimensional regime and present the Bogoliubov excitation spectrum.
Quantum kinetic theory for a condensed bosonic gas Walser, R.; Williams, J.; Cooper, J. ...
Physical review. A, Atomic, molecular, and optical physics,
05/1999, Letnik:
59, Številka:
5
Journal Article
Amorphous wires and ribbons of composition Co/sub 70.5/Fe/sub 4.5/Si/sub 15/B/sub 10/ have a very small magnetostriction and very low coercivities for wall motion. Their high permeabilities are of ...considerable technological interest. Thin films of these alloys might be useful for applications, but had not been previously studied. This work studied the structural and magnetic properties of amorphous thin films sputtered from an alloy target with the composition Co/sub 70.5/Fe/sub 4.5/Si/sub 15/B/sub 10/. The results obtained show that the coercivity and in-plane anisotropy of the sputtered films are much larger than those of ribbons and wires. Attempts to reduce these parameters by varying the processing and annealing parameters, substrate material, composition, and film thickness were largely unsuccessful. While these results are not understood, the composite data suggests that the higher values may be due to micro-compositional inhomogeneities resulting from higher effective quench rates of sputtering.
The correlation between grain morphologies and magnetic properties of CoCrPt/Cr thin films was investigated by varying the sputtering deposition parameters of CoCrPt thin films. Independent of ...sputtering conditions, the Cr underlayer enhanced Co-grain isolation and limited grain growth in CoCrPt films, resulting in increased coercivity. Cross-sectional transmission electron microscopy indicated a strong separation of the Co grains with increasing argon sputtering pressure, due to the enhanced scattering of argon ions by sputtering particles, and thus the observed higher content of Pt in the deposited films. The Co grains separated by 10-20 A thick non-magnetic boundaries were found to grow on a single larger Cr grain, resulting in reduced exchange coupling and increased coercivity. The application of substrate bias increased the (1010) texture of the Co grains and decreased the grain size of the CoCrPt thin films.
Atom interferometry represents a quantum leap in the technology for the ultra-precise monitoring of accelerations and rotations and, therefore, for the science that relies on these quantities. These ...sensors evolved from a new kind of optics based on matter-waves rather than light-waves and might result in an advancement of the fundamental detection limits by several orders of magnitude. This paper describes the current status of the Space Atom Interferometer project (SAI), funded by the European Space Agency. In a multi-pronged approach, SAI aims to investigate both experimentally and theoretically the various aspects of placing atom interferometers in space: the equipment needs, the realistically expected performance limits and potential scientific applications in a micro-gravity environment considering all aspects of quantum, relativistic and metrological sciences. A drop-tower compatible atom interferometry acceleration sensor prototype has been designed, and the manufacturing of its subsystems has been started. A compact modular laser system for cooling and trapping rubidium atoms has been assembled. A compact Raman laser module, featuring outstandingly low phase noise, has been realized. Possible schemes to implement coherent atomic sources in the atom interferometer have been experimentally demonstrated.
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