Manifestation of geometric resonance in current dependence of AC susceptibility for unshunted array of Nb–Alx–Nb Josephson junctions

A pronounced resonance-like structure has been observed in the current dependence of AC susceptibility for two-dimensional array of unshunted Nb–Al_x–Nb Josephson junctions. Using a single-plaquette approximation, we were able to successfully fit our data assuming that resonance structure is related to the geometric (inductive) properties of the array.     

Can two planar sources with the same sets of Stokes parameters generate beams with different degrees of polarization?

It is shown that two stochastic electromagnetic beams that propagate from the source plane z = 0 into the half-space z > 0 may have different degrees of polarization throughout the half-space, even though they have the same sets of Stokes parameters in the source plane. This fact is due to a possible difference in the coherence properties of the field in that plane, but other reasons are also possible. The result is illustrated by an example.     

Low noise 80–115 GHz quasiparticle mixer with small Nb/Al-Oxide/Nb tunnel junctions

Millimeter-wave characterization of a heterodyne receiver using (2 m²) Nb/Al-Ox/Nb Superconducting-Insulator-Superconducting (SIS) junctions arrays is reported. The fabrication of the Nb/Al-Ox/Nb SIS junction arrays as a heterodyne mixer is described. The leakage current of these junctions is below 2A at 4.2K and unmeasurable at 2.5K. The receiver gave a noise temperature Double Side Band (DSB) between 63K and 187K over the frequency range 80 to 115 GHz at the first conversion peak. The results are comparable to those obtained with SIS receivers using well researched lead junctions. Contrary to the lead junctions, our mixer using all Nb junctions have proven remarkably stable with respect to thermal cycling, characteristics which are required for space applications. To our knowledge, this is the most reliable low noise receiver operating in this frequency range.     

Influence of the internal degrees of freedom onJ/ψ suppression

The influence of the internal degrees of freedom on theJ/ψ suppression in relativistic heavy ion collisions is studied in the frame of a quantum-mechanical model. The wave function for the internal motion of ac?c \(\bar c\) pair obeys a time-dependent Schrödinger equation with a potential reflecting the properties of the medium in which the pair is travelling. The initial wave function is evaluated theoretically. An imaginary potential is introduced to account for the loss of probability due to the coupling to theD?c \(\bar D\) channels. TheJ/ψ survival probability is estimated as a function of the time spent inside the plasma. The connection with semi-classical approximations based on the formation time concept is established. The quantum-mechanical effects are exhibited and shown to lead to a smooth perpendicular momentum dependence of theJ/ψ suppression, in agreement with the recent reanalysis of the NA38 data by Gupta and Satz. Several plasma scenarios, including or not the presence of a mixed phase are investigated and the effect of the quantum-mechanical treatment is analyzed for each of them. It is shown that the data do not constraint the plasma scenario very strongly, but indicate the possibility of having a mixed phase with a rather long lifetime.     

Peculiarities of the ferromagnetic resonance in multilayer CoFeZr-α-Si films

The static magnetic properties and ferromagnetic resonance spectra of multilayer CoFeZr-α-Si films with different numbers and thicknesses of magnetic and nonmagnetic layers have been investigated. It is established that the shape of the ferromagnetic resonance spectrum and the resonant fields H _res depend on the thickness of nonmagnetic layers and their total number. The character of changes in the spectrum makes it possible to estimate the quality of layers and interfaces.     

Effect of the image forces on the volt-ampere characteristics of a metal-α-Si contact

In the paper an analytic calculation is carried out of the volt-ampere characteristics of a Schottky barrier diode on amorphous silicon for an exponential distribution of the density of localized states in the mobility gap of -Si. Explicit expressions are written for the volt-ampere characteristics with and without the inclusion of the image forces. It is shown that taking into account the image forces in the case of an intimate contact can lead to a substantial increase in the reverse currents through the diode, at the same time changing slightly the slope of both the forward and reverse branches of the volt-ampere characteristics plotted on a semilogarithmic scale.Translated from Izvestiya Vysshikh Uehebnykh Zavedenii, Fizika, No. 2, pp. 88–92, February, 1985.     

The question of the intermediate order inα-Si∶H

In the present paper, estimates are performed of the main parameters of atomic radial distribution functions in -SiH, which are related to certain characteristics of the internal random field of this disordered heteropolar substance. On the basis of the data obtained the question is discussed of the existence of the intermediate order in the material under consideration.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 16–20, July, 1985.     

Properties of InGaAs/GaAs quantum wells with a δ〈Mn〉-doped layer in GaAs

A method of formation of two-dimensional structures containing a δ〈Mn〉-doped layer in GaAs and an In_xGa_1?x As quantum well (QW) separated by a GaAs spacer of thickness d = 4–6 nm is developed using laser evaporation of a metallic target during MOS hydride epitaxy. It is shown that, up to room temperature, these structures have ferromagnetic properties most likely caused by MnAs clusters. At low temperatures (T _m ～ 30 K), the anomalous Hall effect is revealed to occur. This effect is related to hole scattering by Mn ions in GaAs and to the magnetic exchange between these ions and QW holes, which determines the spin polarization of the holes. The behavior of the negative magnetoresistance of these structures at low temperatures indicates the key role of quantum interference effects.     

Experimental study on the 1.94-μm laser performance of c-Cut Tm:YAP crystal with various doping concentration

The influence of the thulium ion concentration on the 1.94-??m laser performance of c-cut Tm:YAP crystal was investigated in this paper. Three crystals with 3, 4, and 5% Tm³⁺ (atom concentration) were examined at 18°C. Our experimental results showed that, the best power performance was obtained with the 4% Tm:YAP crystal. By using 24.8 W of incident pump power at 795 nm, a maximum of 7.5 W of output power was obtained. The slope efficiency was 48.8%, corresponding to diode-to-Tm conversion efficiency of 30.2%.     

Electron transport properties of ß-phase Co0.50Ti0.50 alloy films with various degrees of long range order

The influence of the structural disorder on the electron transport properties of Co_0.50Ti_0.50 alloy films in a temperature range of 4.2-300 K has been investigated at zero and 0.5 T of magnetic field. The disordered state in the alloy films was obtained by vapor quenching deposition onto substrates cooled by liquid nitrogen. The changes in the transport properties of the alloy films caused by the order-disorder structural transformation and the external magnetic field are explained by the analyses using various models for the electron transport in the disordered systems. Received 18 May 1999 and Received in final form 18 January 2000     

The point ion modified Poisson–Boltzmann theory for a planar electric double layer with different permittivities for the electrode,inner layer and diffuse layer

The planar electric double layer is modelled by an electrode, inner layer and diffuse layer whose constant permittivities differ. A point ion modified Poisson–Boltzmann analysis is made of the model with the ions in the diffuse layer having a distance of closest approach to the electrode, which is greater than the inner layer thickness and mimics the ion radius of a primitive model electrolyte. Comparisons are made with existing Monte Carlo simulations for uncharged and charged electrodes. For 1:1 and 2:1 electrolytes with a charged electrode, the modified Poisson–Boltzmann theory successfully predicts the singlet ion normalised density functions and the mean electrostatic potential. With the uncharged electrode, the neglect of ion size is more critical and the theoretical predictions are now poor at the higher concentrations.     

Pion emission in α-particle interactions with various targets of nuclear emulsion detector

The behavior of relativistic hadron multiplicity for4He-nucleus interactions is investigated. The experiment is carried out at 2.1 A and 3.7 A Ge V(Dubna energy) to search for the incident energy effect on the interactions inside different emulsion target nuclei. Data are presented in terms of the number of emitted relativistic hadrons in both forward and backward angular zones. The dependence on the target size is presented. For this purpose the statistical events are discriminated into groups according to the interactions with H, CNO, Em, and Ag Br target nuclei. The separation of events, into the mentioned groups, is executed based on Glauber's multiple scattering theory approach. Features suggestive of a decay mechanism seem to be a characteristic of the backward emission of relativistic hadrons. The results strongly support the assumption that the relativistic hadrons may already be emitted during the de-excitation of the excited target nucleus, in a behavior like that of compound-nucleus disintegration.Regarding the limiting fragmentation hypothesis beyond 1 A Ge V, the target size is the main parameter affecting the backward production of the relativistic hadron. The incident energy is a principal factor responsible for the forward relativistic hadron production, implying that this system of particle production is a creation system. However, the target size is an effective parameter as well as the projectile size considering the geometrical concept regarded in the nuclear fireball model. The data are analyzed in the framework of the FRITIOF model.     

Gradient doping simulation of perovskite solar cells with CH3NH3Sn1−xPbxI3 as the absorber layer

In this study, we built a perovskite solar cells(PSCs) model with a Au/CuSCN/CH₃NH₃Sn_1−xPb_xI₃/TiO₂/FTO glass structure using the SCAPS program and use polynomial fitting to obtain the relationship between the conduction/valence bands of CH₃NH₃Sn_1−xPb_xI₃ and the x value, which is more complex and accurate than that in any previous research. The influences of thickness, electron and hole mobilities, relative permittivity, effective conduction band density, effective valence band density, and the value of x on the solar cell performance are analyzed. Furthermore, we simulate the situation where the doping concentration changes with the absorption layer depth of the device and a special bandgap is formed. The power conversion efficiency of the device improves from 19.96% to 20.52%, with an open-circuit voltage of 0.776 V, a short-circuit current of 33.79 mA/cm², and a filling factor of 77.39% when double gradient doping is performed. The application value of gradient doping in the device absorption layer is obtained.     

Properties of Soliton-Transported Bio-energy in α-Helix Protein Molecules with Three Channels

We study numerically the propagating properties of soliton-transported bio-energy excited in the α-helix protein molecules with three channels in the cases of the short-time and long-time motions and its features of collision at temperature T = 0 and biological temperature T = 300 K by the dynamic equations in the improved Davydov theory and fourth-order Runge-Kutta method, respectively. From these simulation experiments we see that the new solitons in the improved model can move without dispersion at a constant speed retaining its shape and energy in the cases of motion of both short-time or T = 0 and long time or T = 300 K and can go through each other without scattering in their collisions. In these cases its lifetime is, at least, 120 ps at 300 K, in which the soliton can travel over about 700 amino acid residues. This result is consistent with analytic result obtained by quantum perturbed theory in this model. In the meanwhile, the influences of structure disorder of α-helix protein molecules, including the inhomogeneous distribution of amino acids with different masses and fluctuations of spring constant, dipole-dipole interaction, exciton-phonon coupling constant and diagonal disorder, on the solitons are also studied by the fourth-order Runge-Kutta method. The results show that the soliton still is very robust against the structure disorders and thermal perturbation of proteins at biological temperature 300 K. Therefore we can conclude that the new soliton in the α-helix protein molecules with three channels is a possible carrier of bio-energy transport and the improved model is possibly a candidate for the mechanism of this transport.     

Properties of Soliton-Transported Bio-energy in α-Helix Protein Molecules with Three Channels

We study numerically the propagating properties of soliton-transported bio-energy excited in the α-helix protein molecules with three channels in the cases of the short-time and long-time motions and its features of collision at temperature T = 0 and biological temperature T = 300 K by the dynamic equations in the improved Davydov theory and fourth-order Runge-Kutta method, respectively. From these simulation experiments we see that the new solitons in the improved model can move without dispersion at a constant speed retaining its shape and energy in the cases of motion of both short-time or T = 0 and long time or T = 300 K and can go through each other without scattering in their collisions. In these cases its lifetime is, at least, 120 ps at 300 K, in which the soliton can travel over about 700 amino acid residues. This result is consistent with analytic result obtained by quantum perturbed theory in this model. In the meanwhile, the influences of structure disorder of α-helix protein molecules, including the inhomogeneous distribution of amino acids with different masses and fluctuations of spring constant, dipole-dipole interaction, exciton-phonon coupling constant and diagonal disorder, on the solitons are also studied by the fourth-order Runge-Kutta method. The results show that the soliton still is very robust against the structure disorders and thermal perturbation of proteins at biological temperature 300 K. Therefore we can conclude that the new soliton in the α-helix protein molecules with three channels is a possible carrier of bio-energy transport and the improved model is possibly a candidate for the mechanism of this transport.     

Properties of Nd：YAG Laser with the Nonlinear Absorption of the Intracavity Fullerenes

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Effect of inductive and capacitive coupling on the current–voltage characteristic and electromagnetic radiation from a system of Josephson junctions

We have studied the current–voltage characteristic of a system of long Josephson junctions taking into account the inductive and capacitive coupling. The dependence of the average time derivative of the phase difference on the bias current and spatiotemporal dependences of the phase difference and magnetic field in each junction are considered. The possibility of branching of the current–voltage characteristic in the region of zero field step, which is associated with different numbers of fluxons in individual Josephson junctions, is demonstrated. The current–voltage characteristic of the system of Josephson junctions is compared with the case of a single junction, and it is shown that the observed branching is due to coupling between the junctions. The intensity of electromagnetic radiation associated with motion of fluxons is calculated, and the effect of coupling between junctions on the radiation power is analyzed.     

Quantitative estimates of the content of the metastable Si-XII,Si-III,and α-Si phases of silicon in the areas of indenter impressions

A quantitative estimate is presented of the specific and total volumes of the metastable Si-XII, Si-III, and α-Si phases of silicon in a locally strained (Berkovich pyramid) area. Calculations are performed using experimental data obtained via Raman spectroscopy and in situ registration of the Si-I → Si-II phase transitions of silicon under the indenter.     

Micromagnetic simulation of Sm–Co/α-Fe/Sm–Co trilayers with various angles between easy axes and the film plane

Hysteresis loops and energy products have been calculated systematically by a three-dimensional(3D) software OOMMF for Sm–Co/α-Fe/Sm–Co trilayers with various thicknesses and β, where β is the angle between the easy axis and the field applied perpendicular to the film plane. It is found that trilayers with a perpendicular anisotropy possess considerably larger coercivities and smaller remanences and energy products compared with those with an in-plane anisotropy.Increase of β leads to a fast decrease of the maximum energy product as well as the drop of both remanence and coercivity. Such a drop is much faster than that in the single-phased hard material, which can explain the significant discrepancy between the experiment and the theoretical energy products. Some modeling techniques have been utilized with spin check procedures performed, which yield results in good agreement with the one-dimensional(1D) analytical and experimental data, justifying our calculations. Further, the calculated nucleation fields according to the 3D calculations are larger than those based on the 1D model, whereas the corresponding coercivity is smaller, leading to more square hysteresis loops and better agreement between experimental data and the theory.