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 resis
tance 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.
We show that topological frequency band structures emerge in two-dimensional electromagnetic lattices of metamaterial components without the application of an external magnetic field. The topological nature of the band structure manifests itself by t
he occurrence of exceptional points in the band structure or by the emergence of one-way guided modes. Based on an EM network with nearly flat frequency bands of nontrivial topology, we propose a coupled-cavity lattice made of superconducting transmission lines and cavity QED components which is described by the Janes-Cummings-Hubbard model and can serve as simulator of the fractional quantum Hall effect.
We show that a tetragonal lattice of weakly interacting cavities with uniaxial electromagnetic response is the photonic counterpart of topological crystalline insulators, a new topological phase of atomic band insulators. Namely, the frequency band s
tructure stemming from the interaction of resonant modes of the individual cavities exhibits an omnidirectional band gap within which gapless surface states emerge for finite slabs of the lattice. Due to the equivalence of a topological crystalline insulator with its photonic-crystal analog, the frequency band structure of the latter can be characterized by a $Z_{2}$ topological invariant. Such a topological photonic crystal can be realized in the microwave regime as a three-dimensional lattice of dielectric particles embedded within a continuous network of thin metallic wires.
It is shown theoretically that a nonchiral, two-dimensional array of metallic spheres exhibits optical activity as manifested in calculations of circular dichroism. The metallic spheres occupy the sites of a rectangular lattice and for off-normal inc
idence they show a strong circular-dichroism effect around the surface plasmon frequencies. The optical activity is a result of the rectangular symmetry of the lattice which gives rise to different polarizations modes of the crystal along the two orthogonal primitive lattice vectors. These two polarization modes result in a net polar vector, which forms a chiral triad with the wavevector and the vector normal to the plane of spheres. The formation of this chiral triad is responsible for the observed circular dichroism, although the structure itself is intrinsically nonchiral.
Rigourous calculations of the imaging properties of metamaterials consisting of metal-coated semiconductor nanoparticles are presented. In particular, it is shown that under proper choice of geometric and materials parameters, arrays of such particle
s exhibit negative refractive index within the region of the excitonic resonance of the semiconductor. The occurrence of negative refractive index is predicted by the extended Maxwell-Garnett theory and confirmed by a layer-multiple scattering method for electromagnetic waves. By using the same method it is shown that within the negative refractive-index band, arrays of such nanoparticles amplify the transmitted near-field emitted while simultaneously narrow down its spatial profile leading to subwavelength resolution. The effect of material losses to the imaging properties of the arrays is also addressed.
A rigourous theory for the determination of the van der Waals interactions in colloidal systems is presented. The method is based on fluctuational electrodynamics and a multiple-scattering method which provides the electromagnetic Greens tensor. In p
articular, expressions for the Greens tensor are presented for arbitrary, finite, collections of colloidal particles, for infinitely periodic or defected crystals as well as for finite slabs of crystals. The presented formalism allows for {it ab initio} calculations of the vdW interactions is colloidal systems since it takes fully into account retardation, many-body, multipolar and near-fields effects.
We study the blackbody spectrum from slabs of three-dimensional metallodielectric photonic crystals consisting of gold nanoparticles using an ab initio multiple-scattering method. The spectra are calculated for different photonic-crystal slab thickne
sses, particle radii and hosting materials. We find in particular that such crystals exhibit a broadband emission spectrum above a specific cutoff frequency with emissivity of about 90%. The studied photonic crystals can be used as efficient selective emitters and can therefore find application in thermophotovoltaics and sensing.
