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Stepaniants, A.; Sarkisov, D; Meyerovich, A. E.

doi:10.1023/a:1022584518699

Cited by 5 publications

(1 citation statement)

References 10 publications

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“…We will start from the case of slight roughness for which there are well established methods of calculation of the surface-driven scattering probabilities [6] (see also [11,12] and our earlier application to neutrons in a gravitational trap [13]). Since the geometry of the problem is somewhat different from our previous applications [6,13], the calculation should be modified though the general method remains the same.…”

Section: Scattering Probabilities: Weak Roughnessmentioning

confidence: 99%

Gravitational quantum states of neutrons in a rough waveguide

Meyerovich

Nesvizhevsky²

2006

Phys. Rev. A

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A theory of gravitational quantum states of ultracold neutrons in waveguides with absorbing/scattering walls is presented. The theory covers recent experiments in which the ultracold neutrons were beamed between a mirror and a rough scatterer/absorber. The analysis is based on a recently developed theory of quantum transport along random rough walls which is modified in order to include leaky ͑absorbing͒ interfaces and, more importantly, the low-amplitude high-aperture roughness. The calculations are focused on a regime where the direct transitions into the continuous spectrum above the absorption threshold dominate the depletion of neutrons from the gravitational states and are more efficient than the processes involving the intermediate states. The theoretical results for the neutron count are sensitive to the correlation radius ͑lateral size͒ of surface inhomogeneities and to the ratio of the particle energy to the absorption threshold in the weak-roughness limit. The main impediment for observation of the higher gravitational states is the "overhang" of the particle wave functions which can be overcome only by using scatterers with strong roughness. In general, strong roughness with high amplitude is preferable if one wants just to detect the individual gravitational states, while strongroughness experiments with small amplitude and high aperture are preferable for the quantitative analysis of the data. We also discuss ways to further improve the accuracy of calculations and to optimize the experimental regime.

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Section: Scattering Probabilities: Weak Roughnessmentioning

confidence: 99%

Gravitational quantum states of neutrons in a rough waveguide

Meyerovich

Nesvizhevsky²

2006

Phys. Rev. A

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Unconventional trapping of ultracold neutrons

et al. 1999

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Reflection resonances in surface-disordered waveguides: strong higher-order effects of the disorder

et al. 2014

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We study coherent wave scattering through waveguides with a step-like surface disorder and find distinct enhancements in the reflection coefficients at welldefined resonance values. Based on detailed numerical and analytical calculations, we can unambiguously identify the origin of these reflection resonances to be higher-order correlations in the surface disorder profile which are typically neglected in similar studies of the same system. A remarkable feature of this new effect is that it relies on the longitudinal correlations in the step profile, although individual step heights are random and thus completely uncorrelated. The corresponding resonances are very pronounced and robust with respect to ensemble averaging, and lead to an enhancement of wave reflection by more than one order of magnitude.The problem of scattering off a rough surface is a central topic in physics which occurs for many different types of waves and on considerably different length scales [1][2][3][4]. Phenomena induced by surface corrugations play a major role in the study of acoustic, electromagnetic, and matter waves alike and appear in macroscopic domains such as acoustic oceanography and atmospheric sciences [5,6], but also emerge on much smaller length scales, e.g., for photonic crystals [7], optical fibers and waveguides [8,9], surface plasmon polaritons [10], metamaterials [11], thin metallic films [12-14], layered structures [15], graphene nanoribbons [16,17], nanowires [18][19][20], and confined quantum systems [21,22]. While having a detrimental effect on the performance of many of the above systems, surface roughness can also be put to use, e.g., for the fabrication of high-performance thermoelectric devices [23,24] and for light trapping in silicon solar cells [25]; rough surfaces cause anomalously large persistent currents in metallic rings [26] and provide the necessary scattering potential to manipulate ultra-cold neutrons which are bound by the earthʼs gravity potential [27].In view of this sizeable research effort, it might come as a surprise that even quite fundamental effects emerging in surface-disordered systems are still not fully understood. Consider here, in particular, the problem of wave transmission through a surface-corrugated guiding system which we will study in the following. As demonstrated in detail below, even a very elementary and well-studied model system, consisting of a two-dimensional (2D) waveguide with a step-like surface disorder on either boundary (see figure 1), can only be inadequately described with conventional techniques. The reason why the knowledge on surface-disordered waveguides is still far behind the state of the art for bulk-disordered systems is mainly because of the difficulties arising from the non-homogeneous character of transport via different propagating modes (channels). As was numerically shown in [28], the transmission through multi-mode waveguides depends on many characteristic length scales which are specific for each mode. As a result, one can observe a coexistence of b...

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Untitled

Cited by 5 publications

References 10 publications

Gravitational quantum states of neutrons in a rough waveguide

Gravitational quantum states of neutrons in a rough waveguide

Unconventional trapping of ultracold neutrons

Reflection resonances in surface-disordered waveguides: strong higher-order effects of the disorder

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