11,200 research outputs found
Evolution of a coherent array of Bose-Einstein Condensates in a magnetic trap
We investigate the evolution process of the interference pattern for a
coherent array of Bose-Einstein condensates in a magnetic trap after the
optical lattices are switched off. It is shown that there is a decay and
revival of the density oscillation for the condensates confined in the magnetic
trap. We find that, due to the confinement of the magnetic trap, the
interference effect is much stronger than that of the experiment induced by
Pedri et al. (Phys. Rev. Lett, {\bf 87}, 220401), where the magnetic trap is
switched off too. The interaction correction to the interference effect is also
discussed for the density distribution of the central peak.Comment: RevTex, 17 pages,9 figures. E-mail: [email protected]
Three-dimensional quasi-Tonks gas in a harmonic trap
We analyze the macroscopic dynamics of a Bose gas in a harmonic trap with a
superimposed two-dimensional optical lattice, assuming a weak coupling between
different lattice sites. We consider the situation in which the local chemical
potential at each lattice site can be considered as that provided by the
Lieb-Liniger solution. Due to the weak coupling between sites and the form of
the chemical potential, the three-dimensional ground-state density profile and
the excitation spectrum acquire remarkable properties different from both 1D
and 3D gases. We call this system a quasi-Tonks gas. We discuss the range of
applicability of this regime, as well as realistic experimental situations
where it can be observed.Comment: 4 pages, 3 figures, misprints correcte
Quasi 2D Bose-Einstein condensation in an optical lattice
We study the phase transition of a gas of Rb atoms to quantum degeneracy in
the combined potential of a harmonically confining magnetic trap and the
periodic potential of an optical lattice. For high optical lattice potentials
we observe a significant change in the temperature dependency of the population
of the ground state of the system. The experimental results are explained by
the subsequent formation of quasi 2D condensates in the single lattice sites.Comment: 7 pages (including 3 figures
Antireflective nanotextures for monolithic perovskite silicon tandem solar cells
Recently, we studied the effect of hexagonal sinusoidal textures on the reflective properties of perovskite silicon tandem solar cells using the finite element method FEM . We saw that such nanotextures, applied to the perovskite top cell, can strongly increase the current density utilization from 91 for the optimized planar reference to 98 for the best nanotextured device period 500 nm and peak to valley height 500 nm , where 100 refers to the Tiedje Yablonovitch limit. [D. Chen et al., J. Photonics Energy 8, 022601, 2018 , doi 10.1117 1.JPE.8.022601] In this manuscript we elaborate on some numerical details of that work we validate an assumption based on the Tiedje Yablonovitch limit, we present a convergence study for simulations with the finite element method, and we compare different configurations for sinusoidal nanotexture
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