arXiv subjects

Mário G. Silveirinha

Publications and source records attributed to Mário G. Silveirinha.

79 records · Page 5Linked to original sources

arXiv2015

Optical meta-atom for localization of light with quantized energy

The capacity to confine light into a small region of space is of paramount importance in many areas of modern science. Here, we suggest a mechanism to store a quantized "bit" of light - with a very precise amount of energy - in an open core-shell plasmonic structure ("meta-atom") with a nonlinear optical response. Notwithstanding the trapped light state is embedded in the radiation continuum, its lifetime is not limited by the radiation loss. Interestingly, it is shown that the interplay between the nonlinear response and volume plasmons enables breaking fundamental reciprocity restrictions, and coupling very efficiently an external light source to the meta-atom. The collision of an incident optical pulse with the meta-atom may be used to release the trapped radiation "bit".

physics.optics↗

arXiv2015

Embedded Energy State in an Open Semiconductor Heterostructure

In this paper, we show that HgCdTe heterostructures may support bound electronic states embedded in the continuum, such that the discrete energy spectrum overlaps the continuous spectrum. Although the proposed heterostructures are generally penetrable by an incoming electron wave, it is shown that they may support spatially localized trapped stationary states with an infinite lifetime. We discuss the possibility of a free electron being captured by the proposed open resonator, and present a detailed study of the trapping lifetime in the case of a detuned resonator.

cond-mat.mes-hall↗

arXiv2014

Effective Hamiltonian for electron waves in artificial graphene: A first principles derivation

We propose a first principles effective medium formalism to study the propagation of electron waves in semiconductor heterostructures with a zero-band gap. Our theory confirms that near the K-point the dynamics of a two-dimensional electron gas modulated by an external electrostatic potential with honeycomb symmetry is described by the same pseudospinor formalism and Dirac massless equation as a graphene monolayer. Furthermore, we highlight that even though other superlattices based on semiconductors with a zincblende-type structure can have a zero band-gap and a linear energy-momentum dispersion, the corresponding effective medium Hamiltonian is rather different from that of graphene, and can be based on a single-component wavefunction.

cond-mat.mes-hall↗

arXiv2013

Giant nonlinearity in Zero-Gap Semiconductor Superlattices

Using an effective medium approach, we describe how by combining mercury-cadmium-telluride semiconductor alloys with band gap energies of opposite signs it may be possible to design a superlattice where the electrons have isotropic zero-effective mass and a single valley linear energy-momentum dispersion. We demonstrate that because of the zero-mass property, the superlattice may have a strong nonlinear response under the action of an external electromagnetic field.

cond-mat.mtrl-sci↗

arXiv2012

Macroscopic Electromagnetic Response of Arbitrarily Shaped Spatially Dispersive Bodies formed by Metallic Wires

In media with strong spatial dispersion the electric displacement vector and the electric field are typically linked by a partial differential equation in the bulk region. The objective of this work is to highlight that in the vicinity of an interface the relation between the macroscopic fields cannot be univocally determined from the bulk response of the involved materials, but requires instead the knowledge of internal degrees of freedom of the materials. We derive such relation for the particular case of "wire media", and describe a numerical formalism that enables characterizing the electromagnetic response of arbitrarily shaped spatially dispersive bodies formed by arrays of crossed wires. The possibility of concentrating the electromagnetic field in a narrow spot by tapering a metamaterial waveguide is discussed.

physics.comp-ph↗

arXiv2009

Non-local permittivity from a quasi-static model for a class of wire media

A simple quasi-static model applicable to a wide class of wire media is developed that explains strong non-locality in the dielectric response of wire media in clear physical terms of effective inductance and capacitance per unit length of a wire. The model is checked against known solutions and found to be in excellent agreement with the results obtained by much more sophisticated analytical and numerical methods. Special attention is given to suppression of the spatial dispersion effects in wire media.

cond-mat.mtrl-sci↗

arXiv2008

Effects of Spatial Dispersion on Reflection from Mushroom-type Artificial Impedance Surfaces

Several recent works have emphasized the role of spatial dispersion in wire media, and demonstrated that arrays of parallel metallic wires may behave very differently from a uniaxial local material with negative permittivity. Here, we investigate using local and non-local homogenization methods the effect of spatial dispersion on reflection from the mushroom structure introduced by Sievenpiper. The objective of the paper is to clarify the role of spatial dispersion in the mushroom structure and demonstrate that under some conditions it is suppressed. The metamaterial substrate, or metasurface, is modeled as a wire medium covered with an impedance surface. Surprisingly, it is found that in such configuration the effects of spatial dispersion may be nearly suppressed when the slab is electrically thin, and that the wire medium can be modeled very accurately using a local model. This result paves the way for the design of artificial surfaces that exploit the plasmonic-type response of the wire medium slab.

physics.class-ph↗