6,538 research outputs found
Formation and interaction of resonance chains in the open 3-disk system
In ballistic open quantum systems one often observes that the resonances in
the complex-energy plane form a clear chain structure. Taking the open 3-disk
system as a paradigmatic model system, we investigate how this chain structure
is reflected in the resonance states and how it is connected to the underlying
classical dynamics. Using an efficient scattering approach we observe that
resonance states along one chain are clearly correlated while resonance states
of different chains show an anticorrelation. Studying the phase space
representations of the resonance states we find that their localization in
phase space oscillate between different regions of the classical trapped set as
one moves along the chains and that these oscillations are connected to a
modulation of the resonance spacing. A single resonance chain is thus no WKB
quantization of a single periodic orbits, but the structure of several
oscillating chains arises from the interaction of several periodic orbits. We
illuminate the physical mechanism behind these findings by combining the
semiclassical cycle expansion with a quantum graph model.Comment: 25 pages, 15 figure
Waveguide photonic limiters based on topologically protected resonant modes
We propose a concept of chiral photonic limiters utilising topologically
protected localised midgap defect states in a photonic waveguide. The chiral
symmetry alleviates the effects of structural imperfections and guaranties a
high level of resonant transmission for low intensity radiation. At high
intensity, the light-induced absorption can suppress the localised modes, along
with the resonant transmission. In this case the entire photonic structure
becomes highly reflective within a broad frequency range, thus increasing
dramatically the damage threshold of the limiter. Here we demonstrate
experimentally the principle of operation of such photonic structures using a
waveguide consisting of coupled dielectric microwave resonators.Comment: 6 pages, 4 figure
Microwave fidelity studies by varying antenna coupling
The fidelity decay in a microwave billiard is considered, where the coupling
to an attached antenna is varied. The resulting quantity, coupling fidelity, is
experimentally studied for three different terminators of the varied antenna: a
hard wall reflection, an open wall reflection, and a 50 Ohm load, corresponding
to a totally open channel. The model description in terms of an effective
Hamiltonian with a complex coupling constant is given. Quantitative agreement
is found with the theory obtained from a modified VWZ approach [Verbaarschot et
al, Phys. Rep. 129, 367 (1985)].Comment: 9 pages 5 figur
Experimental Observation of the Spectral Gap in Microwave n-Disk Systems
Symmetry reduced three-disk and five-disk systems are studied in a microwave
setup. Using harmonic inversion the distribution of the imaginary parts of the
resonances is determined. With increasing opening of the systems, a spectral
gap is observed for thick as well as for thin repellers and for the latter case
it is compared with the known topological pressure bounds. The maxima of the
distributions are found to coincide for a large range of the distance to radius
parameter with half of the classical escape rate. This confirms theoretical
predictions based on rigorous mathematical analysis for the spectral gap and on
numerical experiments for the maxima of the distributions.Comment: 5 pages, 4 figure
Schematic baryon models, their tight binding description and their microwave realization
A schematic model for baryon excitations is presented in terms of a symmetric
Dirac gyroscope, a relativistic model solvable in closed form, that reduces to
a rotor in the non-relativistic limit. The model is then mapped on a nearest
neighbour tight binding model. In its simplest one-dimensional form this model
yields a finite equidistant spectrum. This is experimentally implemented as a
chain of dielectric resonators under conditions where their coupling is
evanescent and good agreement with the prediction is achieved.Comment: 17 pages, 15 figure
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Lipid and Protein Transfer between Nanolipoprotein Particles and Supported Lipid Bilayers.
A nanolipoprotein particle (NLP) is a lipid bilayer disc stabilized by two amphipathic "scaffold" apolipoproteins. It has been most notably utilized as a tool for solubilizing a variety of membrane proteins while preserving structural and functional properties. Transfer of functional proteins from NLPs into model membrane systems such as supported lipid bilayers (SLBs) would enable new opportunities, for example, two-dimensional protein crystallization and studies on protein-protein interactions. This work used fluorescence microscopy and atomic force microscopy to investigate the interaction between NLPs and SLBs. When incubated with SLBs, NLPs were found to spontaneously deliver lipid and protein cargo. The impact of membrane composition on lipid exchange was explored, revealing a positive correlation between the magnitude of lipid transfer and concentration of defects in the target SLB. Incorporation of lipids capable of binding specifically to polyhistidine tags encoded into the apolipoproteins also boosted transfer of NLP cargo. Optimal conditions for lipid and protein delivery from NLPs to SLBs are proposed based on interaction mechanisms
On the theory of cavities with point-like perturbations. Part II: Rectangular cavities
We consider an application of a general theory for cavities with point-like
perturbations for a rectangular shape. Hereby we concentrate on experimental
wave patterns obtained for nearly degenerate states. The nodal lines in these
patterns may be broken, which is an effect coming only from the experimental
determination of the patterns. These findings are explained within a framework
of the developed theory.Comment: 14 pages, 3 figure
First experimental realization of the Dirac oscillator
We present the first experimental microwave realization of the
one-dimensional Dirac oscillator, a paradigm in exactly solvable relativistic
systems. The experiment relies on a relation of the Dirac oscillator to a
corresponding tight-binding system. This tight-binding system is implemented as
a microwave system by a chain of coupled dielectric disks, where the coupling
is evanescent and can be adjusted appropriately. The resonances of the finite
microwave system yields the spectrum of the one-dimensional Dirac oscillator
with and without mass term. The flexibility of the experimental set-up allows
the implementation of other one-dimensional Dirac type equations.Comment: 6 figures, 5 page
Dirac Point and Edge States in a Microwave Realization of Tight-Binding Graphene-like Structures
We present a microwave realization of finite tight-binding graphene-like
structures. The structures are realized using discs with a high index of
refraction. The discs are placed on a metallic surface while a second surface
is adjusted atop the discs, such that the waves coupling the discs in the air
are evanescent, leading to the tight-binding behavior. In reflection
measurements the Dirac point and a linear increase close to the Dirac point is
observed, if the measurement is performed inside the sample. Resonances due to
edge states are found close to the Dirac point if the measurements are
performed at the zigzag-edge or at the corner in case of a broken benzene ring.Comment: 4 pages, 6 figure
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