2,291 research outputs found
Shot noise in superconducting junctions with weak link formed by Anderson impurity
A theory is developed to study shot noise in superconducting (SAS) and hybrid
(SAN) junctions with singly occupied Anderson impurity (A) as a weak link. The
zero-frequency DC component of the shot noise spectral density is calculated at
zero temperature as a function of the bias at different Coulomb repulsion
strengths U, and show a remarkable structure resulting from combination of
electron-electron interaction and Andreev reflections.Comment: 4 two column pages including 4 .eps figure
Coherent pulse detection and multi-channel coherent detection based on a single balanced homodyne receiver
The performance of coherent pulse detection (CPD) and multichannel coherent detection (MCCD) based on a single dual-balanced homodyne receiver was experimentally demonstrated using a grating-coupled hybridly mode-locked semiconductor laser. Compared with direct detection, a high coherent gain of over 10 dB, as well as an SNR improvement of over 5 dB, was obtained in both detection schemes. Our experimental results have confirmed that the coherent detection processes in CPD and MCCD are nearly the same based on a square-root LO power dependence. Nevertheless, the MCCD scheme has shown an advantage in a path-length error over the CPD scheme, revealing 2 similar to 3 dB improvement in sensitivities
Planning for Detroit's Tax-Reverted Properties: Possibilities fo rthe Wayne County Land Bank
http://deepblue.lib.umich.edu/bitstream/2027.42/110958/1/planning_for_detroit_s_tax_reverted_properties2006.pd
Subgap anomaly and above-energy-gap structure in chains of diffusive SNS junctions
We present the results of low-temperature transport measurements on chains of
superconductor--normal-constriction--superconductor (SNS) junctions fabricated
on the basis of superconducting PtSi film. A comparative study of the
properties of the chains, consisting of 3 and 20 SNS junctions in series, and
single SNS junctions reveals essential distinctions in the behavior of the
current-voltage characteristics of the systems: (i) the gradual decrease of the
effective suppression voltage for the excess conductivity observed at zero bias
as the quantity of the SNS junctions increases, (ii) a rich fine structure on
the dependences dV/dI-V at dc bias voltages higher than the superconducting gap
and corresponding to some multiples of 2\Delta/e. A model to explain this
above-energy-gap structure based on energy relaxation of electron via
Cooper-pair-breaking in superconducting island connecting normal metal
electrods is proposed.Comment: RevTex, 5 pages, 4 figure
Nonlocal effects in the shot noise of diffusive superconductor - normal-metal systems
A cross-shaped diffusive system with two superconducting and two normal
electrodes is considered. A voltage is applied between the normal
leads. Even in the absence of average current through the superconducting
electrodes their presence increases the shot noise at the normal electrodes and
doubles it in the case of a strong coupling to the superconductors. The
nonequilibrium noise at the superconducting electrodes remains finite even in
the case of a vanishingly small transport current due to the absence of energy
transfer into the superconductors. This noise is suppressed by
electron-electron scattering at sufficiently high voltages.Comment: 4 pages, RevTeX, 2 eps figure
Multiple Andreev Reflection and Giant Excess Noise in Diffusive Superconductor/Normal-Metal/Superconductor Junctions
We have studied superconductor/normal metal/superconductor (SNS) junctions
consisting of short Au or Cu wires between Nb or Al banks. The Nb based
junctions display inherent electron heating effects induced by the high thermal
resistance of the NS boundaries. The Al based junctions show in addition
subharmonic gap structures in the differential conductance dI/dV and a
pronounced peak in the excess noise at very low voltages V. We suggest that the
noise peak is caused by fluctuations of the supercurrent at the onset of
Josephson coupling between the superconducting banks. At intermediate
temperatures where the supercurrent is suppressed a noise contribution ~1/V
remains, which may be interpreted as shot noise originating from large multiple
charges.Comment: 7 pages, 7 figures, extended versio
Full Current Statistics in Diffusive Normal-Superconductor Structures
We study the current statistics in normal diffusive conductors in contact
with a superconductor. Using an extension of the Keldysh Green's function
method we are able to find the full distribution of charge transfers for all
temperatures and voltages. For the non-Gaussian regime, we show that the
equilibrium current fluctuations are enhanced by the presence of the
superconductor. We predict an enhancement of the nonequilibrium current noise
for temperatures below and voltages of the order of the Thouless energy
E_Th=D/L^2. Our calculation fully accounts for the proximity effect in the
normal metal and agrees with experimental data. We demonstrate that the
calculation of the full current statistics is in fact simpler than a concrete
calculation of the noise.Comment: 4 pages, 2 figures (included
Coherent low-energy charge transport in a diffusive S-N-S junction
We have studied the current voltage characteristics of diffusive mesoscopic
Nb-Cu-Nb Josephson junctions with highly-transparent Nb-Cu interfaces. We
consider the low-voltage and high-temperature regime eV<\epsilon_{c}<k_{B}T
where epsilon_{c} is the Thouless energy. The observed excess current as well
as the observed sub-harmonic Shapiro steps under microwave irradiation suggest
the occurrence of low-energy coherent Multiple Andreev Reflection (MAR).Comment: 4 pages, 4 figures, final versio
Two-dimensional array of diffusive SNS junctions with high-transparent interfaces
We report the first comparative study of the properties of two-dimensional
arrays and single superconducting film - normal wire - superconducting film
(SNS) junctions. The NS interfaces of our SNS junctions are really high
transparent, for superconducting and normal metal parts are made from the same
material (superconducting polycrystalline PtSi film). We have found that the
two-dimensional arrays reveal some novel features: (i) the significant
narrowing of the zero bias anomaly (ZBA) in comparison with single SNS
junctions, (ii) the appearance of subharmonic energy gap structure (SGS), with
up to n=16 (eV=\pm 2\Delta/n), with some numbers being lost, (iii) the
transition from 2D logarithmic weak localization behavior to metallic one. Our
experiments show that coherent phenomena governed by the Andreev reflection are
not only maintained over the macroscopic scale but manifest novel pronounced
effects as well. The behavior of the ZBA and SGS in 2D array of SNS junctions
strongly suggests that the development of a novel theoretical approach is
needed which would self-consistently take into account the distribution of the
currents, the potentials, and the superconducting order parameter.Comment: RevTex, 5 pages, 5 figure
Reference standardization and triglyceride interference of a new homogeneous HDL-cholesterol assay compared with a former chemical precipitation assay
A homogeneous HDL-c assay (HDL-H), which uses polyethylene glycol-modified
enzymes and sulfated alpha-cyclodextrin, was assessed for precision,
accuracy, and cholesterol and triglyceride interference. In addition, its
analytical performance was compared with that of a phosphotungstic acid
(PTA)/MgCl2 precipitation method (HDL-P). Within-run CVs were < or =
1.87%; total CVs were < or = 3.08%. Accuracy was evaluated in fresh
normotriglyceridemic sera using the Designated Comparison Method (HDL-H =
1.037 Designated Comparison Method + 4 mg/L; n = 63) and in moderately
hypertriglyceridemic sera by using the Reference Method (HDL-H = 1.068
Reference Method - 17 mg/L; n = 41). Mean biases were 4.5% and 2.2%,
respectively. In hypertriglyceridemic sera (n = 85), HDL-H concentrations
were increasingly positively biased with increasing triglyceride
concentrations. The method comparison between HDL-H and HDL-P yielded the
following equation: HDL-H = 1.037 HDL-P + 15 mg/L; n = 478. We conclude
that HDL-H amply meets the 1998 NCEP recommendations for total error; its
precision is superior compared with that of HDL-P, and its average bias
remains below +/-5% as long as triglyceride concentrations are < or = 10
g/L and in case of moderate hypercholesterolemia
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