5,322 research outputs found
Collective resonances in plasmonic crystals: Size matters
Periodic arrays of metallic nanoparticles may sustain Surface Lattice
Resonances (SLRs), which are collective resonances associated with the
diffractive coupling of Localized Surface Plasmon Resonances (LSPRs). By
investigating a series of arrays with varying number of particles, we traced
the evolution of SLRs to its origins. Polarization resolved extinction spectra
of arrays formed by a few nanoparticles were measured, and found to be in very
good agreement with calculations based on a coupled dipole model. Finite size
effects on the optical properties of the arrays are observed, and our results
provide insight into the characteristic length scales for collective plasmonic
effects: for arrays smaller than 5 x 5 particles, the Q-factors of SLRs are
lower than those of LSPRs; for arrays larger than 20 x 20 particles, the
Q-factors of SLRs saturate at a much larger value than those of LSPRs; in
between, the Q-factors of SLRs are an increasing function of the number of
particles in the array.Comment: 4 figure
(Sp)-1-Diphenylphosphanyl-2-{(S)-[2-(diphenylphosphanyl)phenyl]hydroxymethyl}ferrocene
The absolute configuration of the title compound, [Fe(C5H5)(C36H29OP2)], is Sp at the ferrocene group and S at the asymmetric C atom. Both P atoms have a trigonal-pyramidal conformation. There is a short intramolecular C-H...P contact with an H...P distance of 2.56 Å. The hydroxy group is involved in an intramolecular O-H...[pi]phenyl interaction. The crystal packing shows five very weak intermolecular C-H...[pi] contacts, with H...Cg distances between 3.26 and 3.39 Å (Cg is the centroid of a phenyl or cyclopentadienyl ring). Key indicators: single-crystal X-ray study; T = 162 K; mean σ(C–C) = 0.004 Å; R factor = 0.038; wR factor = 0.083; data-to-parameter ratio = 22.3
Positivity in the presence of initial system-environment correlation
The constraints imposed by the initial system-environment correlation can
lead to nonpositive Dynamical maps. We find the conditions for positivity and
complete positivity of such dynamical maps by using the concept of an
assignment map. Any initial system-environment correlations make the assignment
map nonpositive, while the positivity of the dynamical map depends on the
interplay between the assignment map and the system-environment coupling. We
show how this interplay can reveal or hide the nonpositivity of the assignment
map. We discuss the role of this interplay in Markovian models.Comment: close to the published version. 5 pages, 1 figur
Thermalization and Cooling of Plasmon-Exciton Polaritons: Towards Quantum Condensation
We present indications of thermalization and cooling of quasi-particles, a
precursor for quantum condensation, in a plasmonic nanoparticle array. We
investigate a periodic array of metallic nanorods covered by a polymer layer
doped with an organic dye at room temperature. Surface lattice resonances of
the array---hybridized plasmonic/photonic modes---couple strongly to excitons
in the dye, and bosonic quasi-particles which we call
plasmon-exciton-polaritons (PEPs) are formed. By increasing the PEP density
through optical pumping, we observe thermalization and cooling of the strongly
coupled PEP band in the light emission dispersion diagram. For increased
pumping, we observe saturation of the strong coupling and emission in a new
weakly coupled band, which again shows signatures of thermalization and
cooling.Comment: 8 pages, 5 figures including supplemental material. The newest
version includes new measurements and corrections to the interpretation of
the result
Coherent absorption and enhanced photoluminescence in thin layers of nanorods
We demonstrate a large light absorptance (80%) in a nanometric layer of
quantum dots in rods (QRs) with a thickness of 23 nm. This behavior is
explained in terms of the coherent absorption by interference of the light
incident at a certain angle onto the very thin QR layer. We exploit this
coherent light absorption to enhance the photoluminescent emission from the
QRs. Up to a seven- and fivefold enhancement of the photoluminescence is
observed for p- and s-polarized incident light, respectively.Comment: Physical Review B 201
Power-law decay in first-order relaxation processes
Starting from a simple definition of stationary regime in first-order
relaxation processes, we obtain that experimental results are to be fitted to a
power-law when approaching the stationary limit. On the basis of this result we
propose a graphical representation that allows the discrimination between
power-law and stretched exponential time decays. Examples of fittings of
magnetic, dielectric and simulated relaxation data support the results.Comment: to appear in Phys. Rev. B; 4 figure
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