107 research outputs found
Surface Josephson plasma waves in layered superconductors
We predict the existence of surface waves in layered superconductors in the
THz frequency range, below the Josephson plasma frequency . This wave
propagates along the vacuum-superconductor interface and dampens in both
transverse directions out of the surface (i.e., towards the superconductor and
towards the vacuum). This is the first prediction of propagating surface waves
in any superconductor. These predicted surface Josephson plasma waves are
important for different phenomena, including the complete suppression of the
specular reflection from a sample (Wood's anomalies) and a huge enhancement of
the wave absorption (which can be used as a THz detector).Comment: 4 pages, 2 figure
Layered superconductors as negative-refractive-index metamaterials
We analyze the use of layered superconductors as anisotropic metamaterials.
Layered superconductors can have a negative refraction index in a wide
frequency range for arbitrary incident angles. Indeed, low-Tc (s-wave)
superconductors allow to produce artificial heterostructures with low losses
for T<<Tc. However, the real part of their in-plane effective permittivity is
very large. Moreover, even at low temperatures, layered high-Tc superconductors
have a large in-plane normal conductivity, producing large losses (due to
d-wave symmetry). Therefore, it is difficult to enhance the evanescent modes in
either low-Tc or high-Tc superconductors.Comment: 4 pages, 2 figure
Conversion of terahertz wave polarization at the boundary of a layered superconductor due to the resonance excitation of oblique surface waves
We predict a complete TM-TE transformation of the polarization of terahertz
electromagnetic waves reflected from a strongly anisotropic boundary of a
layered superconductor. We consider the case when the wave is incident on the
superconductor from a dielectric prism separated from the sample by a thin
vacuum gap. The physical origin of the predicted phenomenon is similar to the
Wood anomalies known in optics, and is related to the resonance excitation of
the oblique surface waves. We also discuss the dispersion relation for these
waves, propagating along the boundary of the superconductor at some angle with
respect to the anisotropy axis, as well as their excitation by the
attenuated-total-reflection method.Comment: 4 pages, 5 figure
Competition between Two Kinds of Correlations in Literary Texts
A theory of additive Markov chains with long-range memory is used for
description of correlation properties of coarse-grained literary texts. The
complex structure of the correlations in texts is revealed. Antipersistent
correlations at small distances, L 300 define
this nontrivial structure. For some concrete examples of literary texts, the
memory functions are obtained and their power-law behavior at long distances is
disclosed. This property is shown to be a cause of self-similarity of texts
with respect to the decimation procedure.Comment: 7 pages, 7 figures, Submitted to Physica
Inhomogeneous DNA: conducting exons and insulating introns
Parts of DNA sequences known as exons and introns play very different role in
coding and storage of genetic information. Here we show that their conducting
properties are also very different. Taking into account long-range correlations
among four basic nucleotides that form double-stranded DNA sequence, we
calculate electron localization length for exon and intron regions. Analyzing
different DNA molecules, we obtain that the exons have narrow bands of extended
states, unlike the introns where all the states are well localized. The band of
extended states is due to a specific form of the binary correlation function of
the sequence of basic DNA nucleotides.Comment: 14 pages, 6 figure
Response of HTS tapes to a parallel ac magnetic field in the vicinity of the superconducting transition
We have studied the temperature dependence of the ac magnetic susceptibility χ(T) = χ′(T) + iχ″(T) of YBCO tapes in a parallel magnetic field in both the Meissner and vortex states. For the vortex state, we have observed two maximums in the χ″(T) dependence. The position and the magnitude of one of these maxima are described well by the nonlocal critical state model. The second maximum and corresponding kink in the function χ′(T) observed close to the temperature Tc of the superconducting transition are unexpected. The origin of this maximum cannot be explained within the usual notions of the high-temperature superconductivity. We suppose that it is related to some magnetic restructuring in the superconducting layer just above Tc. Our results put a question on the correctness of the interpretation of some previous microwave experiments
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Layered superconductors as negative-refractive-index metamaterials
We analyze the use of layered superconductors as strongly anisotropic metamaterials, which can possess negative-refractive-index in a wide frequency range. Superconductors are of particular interest because they have the potential to support low losses, which is critical for applications such as super-resolution imaging. We show that low-Tc (s-wave) superconductors can be used to construct layered heterostructures with low losses for . However, the real part of their in-plane effective permittivity is very large, making coupling into the structure difficult. Moreover, even at low temperatures, layered high-Tc superconductors have a large in-plane normal conductivity, producing large losses (due to d-wave symmetry). Therefore, it is difficult to enhance the evanescent modes in either low-Tc or high-Tc superconductorsEngineering and Applied Science
Additive N-Step Markov Chains as Prototype Model of Symbolic Stochastic Dynamical Systems with Long-Range Correlations
A theory of symbolic dynamic systems with long-range correlations based on
the consideration of the binary N-step Markov chains developed earlier in Phys.
Rev. Lett. 90, 110601 (2003) is generalized to the biased case (non equal
numbers of zeros and unities in the chain). In the model, the conditional
probability that the i-th symbol in the chain equals zero (or unity) is a
linear function of the number of unities (zeros) among the preceding N symbols.
The correlation and distribution functions as well as the variance of number of
symbols in the words of arbitrary length L are obtained analytically and
verified by numerical simulations. A self-similarity of the studied stochastic
process is revealed and the similarity group transformation of the chain
parameters is presented. The diffusion Fokker-Planck equation governing the
distribution function of the L-words is explored. If the persistent
correlations are not extremely strong, the distribution function is shown to be
the Gaussian with the variance being nonlinearly dependent on L. An equation
connecting the memory and correlation function of the additive Markov chain is
presented. This equation allows reconstructing a memory function using a
correlation function of the system. Effectiveness and robustness of the
proposed method is demonstrated by simple model examples. Memory functions of
concrete coarse-grained literary texts are found and their universal power-law
behavior at long distances is revealed.Comment: 19 pages, 8 figure
Surface Plasma Waves Across the Layers of Intrinsic Josephson Junctions
We predict surface electromagnetic waves propagating across the layers of
intrinsic Josephson junctions. We find the spectrum of the surface waves and
study the distribution of the electromagnetic field inside and outside the
superconductor. The profile of the amplitude oscillations of the electric field
component of such waves is peculiar: initially, it increases toward the center
of the superconductor and, after reaching a crossover point, decreases
exponentially.Comment: 11 pages, 5 figure
Resonance effects due to the excitation of surface Josephson plasma waves in layered superconductors
We analytically examine the excitation of surface Josephson plasma waves
(SJPWs) in periodically-modulated layered superconductors. We show that the
absorption of the incident electromagnetic wave can be substantially increased,
for certain incident angles, due to the resonance excitation of SJPWs. The
absorption increase is accompanied by the decrease of the specular reflection.
Moreover, we find the physical conditions guaranteeing the total absorption
(and total suppression of the specular reflection). These conditions can be
realized for Bi2212 superconductor films.Comment: 17 pages, 3 figure
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