On the applicability of non-resonant artificial diamagnetics

Artificial diamagnetics are prominent for achieving extraordinarily strong diamagnetism in a wide frequency range. However, as far as the magnetic fields outside the artificial medium are concerned, bulk conductors show a very similar pattern. The question arises whether the complicated internal structure of artificial diamagnetics can, to this end, be replaced by a simpler object. We analyse the figure of merit for the application of diamagnetics in magnetic levitation, and show that for an electrically small body, any internal structuring makes the figure of merit worse than that of a simple conducting object.Comment: 5 pages, 5 figure

Loan Participations and the Savings and Loan Association: A Sleeping Giant Stirs

Savings institutions have believed themselves to be secure in their mortgage trading practices, but recent failures of financial institutions and the entry into the mortgage market of non-regulated, non-banking entities have prompted some much needed re-examination of the real risks and the character of the legal relationships which arise from such transactions. This article shall identify those risks, particularly the insolvency of the originating lender, and the resulting consequences which may be visited upon the investing savings institutions

Slow convergence to effective medium in finite discrete metamaterials

© 2016 American Physical Society. It is known that metamaterial properties may differ significantly from the predictions of effective-medium theory. In many cases this is due to the finite size and discrete structure, which cannot be neglected in practical samples with a relatively small amount of elements. We analyze the response of finite discrete metamaterial objects of a spherical shape and demonstrate the role of boundary effects in these structures, pointing out an interplay between the size of the structure and the dissipation. We conclude that the discrepancy between the actual resonance frequency of a sphere and the effective-medium prediction is inversely proportional to the size of the sphere

On the deviation of metamaterial spheres from effective medium

© 2016 IEEE. We analyse the convergence of the actual properties of finite subwavelength metamaterial samples where all the prerequisites for a reliable effective medium description, except for the finite size, are fulfilled, towards the effective medium predictions. We show that the convergence is rather slow and it is likely that hundreds of thousands of individual meta-atoms must be assembled together before the properties of the resulting structure can be claimed to correspond to those a bulk material. These observations are directly relevant for practical design of metamaterials and their future development

Self-oscillations in nonlinear torsional metamaterials

We study the nonlinear dynamics of torsional meta-molecules - sub-wavelength resonators with strong coupling between electromagnetic excitation and rotational deformation - and show that such structures may undergo self-oscillations. We develop a semi-analytical model to evaluate the electromagnetic-elastic coupling in such structures. By analysing the local stability of the system, we reveal two different mechanisms leading to self-oscillations. Contrary to many previously studied optomechanical systems, self-oscillations of torsional meta-molecules can be extremely robust against mechanical damping. Due to the chiral nature of the structure, a consequence of self-oscillations in this system is dynamic nonlinear optical activity, which can be actively controlled by a range of parameters such as the field strength and polarization of the incident wave. © IOP Publishing and Deutsche Physikalische Gesellschaft

Nonlocal homogenization for nonlinear metamaterials

©2016 American Physical Society. 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 analyzing resonant nonlinear metamaterials