30 research outputs found
Matter-Wave Tractor Beams
Optical and acoustic tractor beams are currently the focus of intense research due to their counterintuitive property of exerting a pulling force on small scattering objects. In this Letter we propose a matter-wave tractor beam and utilize the de Broglie waves of nonrelativistic matter particles in analogy to “classical” tractor beams. We reveal the presence of the quantum-mechanical pulling force for the variety of quantum mechanical potentials observing the resonant enhancement of the pulling effect under the conditions of the suppressed scattering known as the Ramsauer-Townsend effect. We also derive the sufficient conditions on the scattering potential for the emergence of the pulling force and show that, in particular, a Coulomb scatterer is always shoved, while a Yukawa (screened Coulomb) scatterer can be drawn. Pulling forces in optics, acoustics, quantum mechanics, and classical mechanics are compared, and the matter-wave pulling force is found to have exclusive properties of dragging slow particles in short-range potentials. We envisage that the use of tractor beams could lead to the unprecedented precision in manipulation with atomic-scale quantum objects
Nonlocal homogenization for nonlinear metamaterials
We present a consistent theoretical approach for calculating effective
nonlinear susceptibilities of metamaterials taking into account both frequency
and spatial dispersion. Employing the discrete dipole model, we demonstrate
that effects of spatial dispersion become especially pronounced in the vicinity
of effective permittivity resonance where nonlinear susceptibilities reach
their maxima. In that case spatial dispersion may enable simultaneous
generation of two harmonic signals with the same frequency and polarization but
different wave vectors. We also prove that the derived expressions for
nonlinear susceptibilities transform into the known form when spatial
dispersion effects are negligible. In addition to revealing new physical
phenomena, our results provide useful theoretical tools for analysing resonant
nonlinear metamaterials