16 research outputs found
Mobility Edge in Aperiodic Kronig-Penney Potentials with Correlated Disorder: Perturbative Approach
It is shown that a non-periodic Kronig-Penney model exhibits mobility edges
if the positions of the scatterers are correlated at long distances. An
analytical expression for the energy-dependent localization length is derived
for weak disorder in terms of the real-space correlators defining the
structural disorder in these systems. We also present an algorithm to construct
a non-periodic but correlated sequence exhibiting desired mobility edges. This
result could be used to construct window filters in electronic, acoustic, or
photonic non-periodic structures.Comment: RevTex, 4 pages including 2 Postscript figure
Economic Impact of Expanded Use of Biologic Therapy for Crohn’s Disease In Latin American Countries
PGI5 Economic Impact of Expanded Use of Biologic Therapy for Crohn’s Disease In Latin American Countries
Metafluid with anisotropic dynamic mass
We show that a fluid filling the space between metallic cylinders arranged in a two-dimensional lattice exhibits anisotropic dynamic mass for sound waves propagating through the lattice, if its unit cell is anisotropic. Using the plane-waves expansion method we derive (in the long wavelength limit) a formula for the effective mass tensor of the metafluid. The proposed formula is very general — it is valid for arbitrary Bravais lattices and arbitrary filling fractions of the cylinders. We apply our method to a periodic structure with very high anisotropy, when other known methods fail. In particular, we calculate the effective mass tensor for sound waves in air with embedded lattice of aluminum cylinders having rectangular cross sections, and obtain excellent agreement with experiment. The proposed method of calculation may find numerous applications for tailoring of metafluids with prescribed anisotropy
Index of refraction of a photonic crystal of carbon nanotubes and homogenization of optically anisotropic periodic composites
We consider the long-wavelength limit for a periodic arrangement of carbon nanotubes. Using the Fourier
expansion method we develop an effective-medium theory for photonic crystal of aligned optically
anisotropic cylinders. Exact analytical formulas for the effective dielectric constants for the E and H
eigenmodes are obtained for arbitrary 2D Bravais lattice and arbitrary cross-section of anisotropic cylinders.
It is shown that depending on the symmetry of the unit cell photonic crystal of anisotropic cylinders behaves
in the low-frequency limit like uniaxial or biaxial optical crystal. The developed theory of homogenization
is in a good agreement with existing experimental results for the dielectric tensor of photonic crystals
of carbon nanotubes