Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userArrays of carbon nanoscrolls as deep-subwavelength magnetic metamaterials
115
0
0.0
(
0
)
Added by
Vassilios Yannopapas
Publication date
2013
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We demonstrate theoretically that an array of carbon nanoscrolls acts as a hyperbolic magnetic metamaterial in the THz regime with genuine subwavelength operation corresponding to wavelength-to-structure ratio of about 200. Due to the low sheet resistance of graphene, the electromagnetic losses in an array of carbon nanoscrolls are almost negligible offering a very sharp magnetic resonance of extreme positive and negative values of the effective magnetic permeability. The latter property leads to superior imaging properties for arrays of carbon nanoscrolls which can operate as magnetic endoscopes in the THz where magnetic materials are scarce. Our optical modelling is supplemented with ab initio density-functional calculations of the self-winding of a single layer of graphene onto a carbon nanotube so as to form a carbon nanoscroll. The latter process is viewed as a means to realize ordered arrays of carbon nanoscrolls in the laboratory based on arrays of aligned carbon nanotubes which are nowadays routinely fabricated.
rate research
Read More
We study by first-principles calculations the electro-mechanical response of carbon nanoscrolls. We show that although they present a very similar behavior to carbon nanotubes for what concerns the axial deformation sensitivity, they exhibit a radial response upon charge injection which is up to one order of magnitude larger. In association with their high stability, this behavior make them a natural choice for a new class of very efficient nano-actuators.
We have studied the plasmonic properties of aperiodic arrays of identical nanoparticles (NPs) formed by two opposite and equal graded-chains (a chain where interactions change gradually). We found that these arrays concentrate the external electromagnetic fields even in the long wavelength limit. The phenomenon was understood by identifying the system with an effective cavity where plasmonics excitations are trapped between effective band edges, resulting from the change of passband with NPs position. Dependence of excitation concentration on several systems parameter was also assessed. This includes, different gradings as well as NPs couplings, damping, and resonant frequencies. In the spirit of the scaling laws in condensed matter physics, we developed a theory that allows us to rationalize all these systems parameters into universal curves. The theory is quite general and can also be used on many other situations (different arrays for example). Additionally, we also provided an analytical solution, in the tight-binding limit, for the plasmonic response of homogeneous linear chains of NPs illuminated by a plane wave. Our results can find applications on sensing, near field imaging, plasmon-enhanced photodetectors, as well as to increase solar cell efficiency.
We theoretically investigate the magnetic response of two-dimensional arrays of superconducting strips, which are regarded as essential structures of dc magnetic metamaterials. We analytically obtain local distributions of the magnetic field for the ideal complete shielding state (i.e., $Lambda/wto 0$, where $2w$ is the strip width, $Lambda=lambda^2/d$ is the Pearl length, $lambda$ is the London penetration depth, and $d$ is the strip thickness), and derive effective permeability by averaging the local field distributions. We also perform numerical calculations for a realistic case, taking finite $Lambda/w>0$ into account. We investigate two types of strip arrays: a rectangular array and a hexagonal array. The resulting effective permeability has large anisotropy that depends on the dimensions and arrangement of the superconducting strips, and the hexagonal array is found to be more advantageous for obtaining large anisotropy than the rectangular array.
We have theoretically investigated the magnetic response of two-dimensional (2D) arrays of superconducting and soft magnetic strips, which are regarded as models of dc magnetic metamaterials. The anisotropy of the macroscopic permeabilities depends on whether the applied magnetic field is parallel to the wide surface of the strips ($mu_{parallel}$) or perpendicular ($mu_{perp}$). For the 2D arrays of superconducting strips, $0<mu_{perp}/mu_0ll mu_{parallel}/mu_0simeq 1$, whereas for the 2D arrays of soft magnetic strips, $mu_{parallel}/mu_0ggmu_{perp}/mu_0simeq 1$, where $mu_0$ is the vacuum permeability. We also demonstrate that strong anisotropy of the macroscopic permeability can be obtained for hybrid arrays of superconducting and soft magnetic strips, where $mu_{parallel}/mu_0gg 1gg mu_{perp}/mu_0>0$.
Topological valley photonics has emerged as a new frontier in photonics with many promising applications. Previous valley boundary transport relies on kink states at internal boundaries between two topologically distinct domains. However, recent studies have revealed a novel class of topological chiral edge states (CESs) at external boundaries of valley materials, which have remained elusive in photonics. Here, we propose and experimentally demonstrate the topological CESs in valley photonic metamaterials (VPMMs) by accurately tuning on-site edge potentials. Moreover, the VPMMs work at deep-subwavelength scales. Thus, the supported CESs are highly confined and self-guiding without relying on a cladding layer to prevent leakage radiation. Via direct near-field measurements, we observe the bulk bandgap, the edge dispersions, and the robust edge transport passing through sharp corners, which are hallmarks of the CESs. Our work paves a way to explore novel topological edge states in valley photonics and sheds light on robust and miniaturized photonic devices.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
