100 research outputs found
Optical "fingerprints" of dielectric resonators
The complete picture of the optical properties of resonant structures, along
with the frequency, quality factor, and line shape in the scattering spectra,
is determined by the electromagnetic field distribution patterns, which are a
kind of "fingerprint" of each resonant eigenmode. In this paper, we
simultaneously analyze the changes in the spectra and the transformation of the
field pattern during the topological transitions from a thin disk to a ring
with a gradually increasing thickness and further to a split ring. In addition,
we demonstrate characteristic optical fingerprints for well-known interference
effects such as bound states in the continuum and Fano resonances.Comment: 11 pages, 5 figure
Fano Resonance Between Mie and Bragg Scattering in Photonic Crystals
We report the observation of a Fano resonance between continuum Mie
scattering and a narrow Bragg band in synthetic opal photonic crystals. The
resonance leads to a transmission spectrum exhibiting a Bragg dip with an
asymmetric profile, which can be tunably reversed to a Bragg rise. The Fano
asymmetry parameter is linked with the dielectric contrast between the
permittivity of the filler and the specific value determined by the opal
matrix. The existence of the Fano resonance is directly related to disorder due
to non-uniformity of a-SiO2 opal spheres. Proposed theoretical "quasi-3D" model
produces results in excellent agreement with the experimental data
Influence of the pseudogap on the superconductivity-induced phonon renormalization in high-T superconductors
We investigate the influence of a d-density wave (DDW) gap on the
superconductivity-induced renormalization of phonon frequency and linewidth.
The results are discussed with respect to Raman and inelastic neutron
scattering experiments. It turns out that the DDW gap can enhance the range of
frequencies for phonon softening depending on the underlying band
structure. Moreover we show that an anisotropic 'd-wave' pseudogap can also
contribute to the q-dependent linewidth broadening of the 340cm phonon
in YBaCuO.Comment: 4 page
Fabrication of submicron structures by three-dimensional laser lithography
As a demonstration of unique capabilities of three dimensional laser lithography, an example complex shape
microobject and photonic crystals with “woodpile” structure for the infrared spectral range are fabricated by
this technique. Photonic dispersion relations for the woodpile structure are calculated for different values of
the permittivity contrast and the filling factor.This study was partially supported by the
Government of the Russian Federation (project no.
074U01) and the Russian Foundation for Basic
Research (project no. 130200186)
Superconducting Gap and Strong In-Plane Anisotropy in Untwinned YBa2Cu3O7-d
With significantly improved sample quality and instrumental resolution, we
clearly identify in the (pi,0) ARPES spectra from YBa2Cu3O6.993, in the
superconducting state, the long-sought `peak-dip-hump' structure. This advance
allows us to investigate the large a-b anisotropy of the in-plane electronic
structure including, in particular, a 50% difference in the magnitude of the
superconducting gap that scales with the energy position of the hump feature.
This anisotropy, likely induced by the presence of the CuO chains, raises
serious questions about attempts to quantitatively explain the YBa2Cu3O7-d data
from various experiments using models based on a perfectly square lattice.Comment: Phys. Rev. Lett., in press. Revtex, 4 pages, 4 postscript figures
embedded in the tex
Superconductivity-induced Resonance Raman Scattering in Multi-layer High-Tc Superconductors
Resonant Raman scattering below Tc has been discovered in several Bi-, Hg-,
Tl-based high-Tc superconductors with three or four CuO2-layers. For
Bi2Si2Ca2Cu3O10+d, we found an unexpected crossover of the pair-breaking peak
in the A1g-spectrum from a broad bump at hw = 6kBTc for Eexc = 2.54eV to a
sharp peak at hw = 8kBTc for Eexc = 2.18eV, together with a strong enhancement
of the Ca-phonons. Under resonant conditions, the relative positions of the
pair breaking peaks in A1g, B1g, and B2g channels are 2Delta(A1g) = 2Delta(B1g)
> 2Delta(B2g). This relation implies that the A1g Raman channel is free from
the Coulomb screening effect, just as predicted theoretically for a d-wave
multi-layer superconductor but have never been observed experimentally thus
far. The observed resonance effect is the evidence that the electronic state in
the inner CuO2-planes is different from that of the outer CuO2-planes.Comment: 16 pages, 6 figures. submitted to Phys.Rev.
Raman scattering in C_{60} and C_{48}N_{12} aza-fullerene: First-principles study
We carry out large scale {\sl ab initio} calculations of Raman scattering
activities and Raman-active frequencies (RAFs) in
aza-fullerene. The results are compared with those of .
Twenty-nine non-degenerate polarized and 29 doubly-degenerate unpolarized RAFs
are predicted for . The RAF of the strongest Raman
signal in the low- and high-frequency regions and the lowest and highest RAFs
for are almost the same as those of .
The study of reveals the importance of electron correlations and
the choice of basis sets in the {\sl ab initio} calculations. Our best
calculated results for with the B3LYP hybrid density functional
theory are in excellent agreement with experiment and demonstrate the desirable
efficiency and accuracy of this theory for obtaining quantitative information
on the vibrational properties of these molecules.Comment: submitted to Phys.Rev.
Inelastic Light Scattering From Correlated Electrons
Inelastic light scattering is an intensively used tool in the study of
electronic properties of solids. Triggered by the discovery of high temperature
superconductivity in the cuprates and by new developments in instrumentation,
light scattering both in the visible (Raman effect) and the X-ray part of the
electromagnetic spectrum has become a method complementary to optical
(infrared) spectroscopy while providing additional and relevant information.
The main purpose of the review is to position Raman scattering with regard to
single-particle methods like angle-resolved photoemission spectroscopy (ARPES),
and other transport and thermodynamic measurements in correlated materials.
Particular focus will be placed on photon polarizations and the role of
symmetry to elucidate the dynamics of electrons in different regions of the
Brillouin zone. This advantage over conventional transport (usually measuring
averaged properties) indeed provides new insights into anisotropic and complex
many-body behavior of electrons in various systems. We review recent
developments in the theory of electronic Raman scattering in correlated systems
and experimental results in paradigmatic materials such as the A15
superconductors, magnetic and paramagnetic insulators, compounds with competing
orders, as well as the cuprates with high superconducting transition
temperatures. We present an overview of the manifestations of complexity in the
Raman response due to the impact of correlations and developing competing
orders. In a variety of materials we discuss which observations may be
understood and summarize important open questions that pave the way to a
detailed understanding of correlated electron systems.Comment: 62 pages, 48 figures, to appear in Rev. Mod. Phys. High-resolution
pdf file available at http://onceler.uwaterloo.ca/~tpd/RMP.pd
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