1,525 research outputs found
Bound States in the Continuum and Fano Resonances in the Dirac Cone Spectrum
We consider light scattering by two dimensional arrays of high-index
dielectric spheres arranged into the triangular lattice. It is demonstrated
that in the case a triple degeneracy of resonant leaky modes in the Gamma-point
the scattering spectra exhibit a complicated picture of Fano resonances with
extremely narrow line-width. The Fan features are explained through coupled
mode theory for a Dirac cone spectrum as a signature of optical bound states in
the continuum (BIC). It is found that the standing wave in-Gamma BIC induces a
ring of off-Gamma BICs due to different scaling laws for real and imaginary
parts of the resonant eigenfrequencies in the Dirac cone spectrum. A
quantitative theory of the spectra is proposed
A hybrid approach for predicting the distribution of vibro-acoustic energy in complex built-up structures
Finding the distribution of vibro-acoustic energy in complex built-up
structures in the mid-to-high frequency regime is a difficult task. In
particular, structures with large variation of local wavelengths and/or
characteristic scales pose a challenge referred to as the mid-frequency
problem. Standard numerical methods such as the finite element method (FEM)
scale with the local wavelength and quickly become too large even for modern
computer architectures. High frequency techniques, such as statistical energy
analysis (SEA), often miss important information such as dominant resonance
behaviour due to stiff or small scale parts of the structure. Hybrid methods
circumvent this problem by coupling FEM/BEM and SEA models in a given built-up
structure. In the approach adopted here, the whole system is split into a
number of subsystems which are treated by either FEM or SEA depending on the
local wavelength. Subsystems with relative long wavelengths are modelled using
FEM. Making a diffuse field assumption for the wave fields in the short wave
length components, the coupling between subsystems can be reduced to a weighted
random field correlation function. The approach presented results in an
SEA-like set of linear equations which can be solved for the mean energies in
the short wavelength subsystems
Phonon assisted tunneling in Josephson junctions
The expression for additional subgap current in the presence of
electron-phonon interaction is derived. We show that the phonon assisted
tunneling leads to appearance of peaks on current-voltage characteristics at
the Josephson frequencies corresponding to the Raman-active phonons. The
relation of the obtained results to experimental observations are discussed.Comment: 8 pages, submitted to PR
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