A many-particle system must posses long-range interactions in order to be hyperuniform at thermal equilibrium. Hydrodynamic arguments and numerical simulations show, nevertheless, that a three-dimensional elastic-line array with short-ranged repulsive interactions, such as vortex matter in a type-II superconductor, forms at equilibrium a class-II hyperuniform two-dimensional point pattern for any constant-z cross section. In this case, density fluctuations vanish isotropically as ∼ q α at small wave-vectors q, with α = 1. This prediction includes the solid and liquid vortex phases in the ideal clean case, and the liquid in presence of weak uncorrelated disorder. We also show that the three-dimensional Bragg glass phase is marginally hyperuniform, while the Bose glass and the liquid phase with correlated disorder are expected to be non-hyperuniform at equilibrium. Furthermore, we compare these predictions with experimental results on the large-wavelength vortex density fluctuations of magnetically decorated vortex structures nucleated in pristine, electron-irradiated and heavy-ion irradiated superconducting Bi2Sr2CaCu2O 8+δ samples in the mixed state. For most cases we find hyperuniform two-dimensional point patterns at the superconductor surface with an effective exponent α eff ≈ 1. We interpret these results in terms of a large-scale memory of the high-temperature line-liquid phase retained in the glassy dynamics when field-cooling the vortex structures into the solid phase. We also discuss the crossovers expected from the dispersivity of the elastic constants at intermediate length-scales, and the lack of hyperuniformity in the xy plane for lengths q −1 larger than the sample thickness due to finite-size effects in the z-direction. We argue these predictions may be observable and propose further imaging experiments to test them independently.arXiv:1907.00394v1 [cond-mat.dis-nn]
Discretized vortex-producing lenses programmed on low performance spatial light modulators have been used for the generation of optical vortices. However, the description of these vortices has been supported only by numerical simulations. In this work, a general analytical treatment (any topological charge -any discretization levels) for the propagation of a Gaussian beam through a discretized vortex-producing lens is presented. The resulting field could be expressed as a sum of Kummer beams with different amplitudes and topological charges focalized at different planes, whose characteristics of formation can be modified by tuning the parameters of the setup. Likewise, vortex lines are analyzed to understand the mechanism of formation of observed topological charges, which appear in specific planes. Conservation of the topological charge is demonstrated. Theoretical predictions are supported by experiments.PACS numbers: 42.25.Fx,42.30.Kq.
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