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Yu. M. Shukrinov

Publications and source records attributed to Yu. M. Shukrinov.

At least 55 records · Page 3Linked to original sources
arXiv2014

Shapiro Step on the rc-Branch in the IV-characteristic of a Josephson Junction with an LC-shunting

The effect of external radiation on the phase dynamics of Josephson junctions shunted by an LC circuit is examined. It is shown that additional resonant circuit (rc) branches appear in the current voltage characteristics of the junctions when the Josephson frequency is equal to the frequency of the formed resonance circuit. We show that the amplitude dependence of the Shapiro step width crucially changes when the Shapiro step is on the rc-branch in comparison to the case of Josephson junction without shunt. The experimental implementation of these effects might give very important advantages for existing methods and technologies.

cond-mat.supr-con↗
arXiv2014

Structured Chaos in a Devil's Staircase of the Josephson Junction

The phase dynamics of Josephson junctions under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents and Poincare sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of +-0.012. The chaotic regions exhibit scaling similarity and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally the influence of the radiation and Josephson junction parameters on the structured chaos is investigated and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.

cond-mat.supr-con↗
arXiv2013

Devil's Staircases and Continued Fractions in the Josephson Junctions

The detailed numerical simulations of the IV-characteristics of Josephson junction under external electromagnetic radiation show devil's staircases within different bias current intervals. We have found that the observed steps form very precisely continued fractions. Increasing of the amplitude of radiation shifts the devil's staircases to higher Shapiro steps. The algorithm of appearing and detection of the subharmonics with increasing radiation amplitude is proposed. We demonstrate that subharmonic steps registered in the famous experiments by A. H. Dayem and J. J. Wiegand [Phys. Rev 155, 419 (1967)] and J. Clarke [Phys. Rev. B 4, 2963 (1971)] also form continued fractions.

cond-mat.supr-con↗
arXiv2013

Breathing Charge Density Waves in Intrinsic Josephson Junctions

We demonstrate the creation of a charge density wave (CDW) along a stack of coupled Josephson junctions in layered superconductors. Electric charge in each superconducting layer oscillates around some average value, forming a breathing CDW. We show the transformation of a longitudinal plasma wave to CDW in the state corresponding to the outermost branch. Transitions between different types of CDW's related to the inner branches of current voltage characteristics are demonstrated. The effect of the external electromagnetic irradiation on the states corresponding to the inner branches differs crucially from the case of the single Josephson junction. The Shapiro steps in the IV-characteristics of the junctions in the stack do not correspond directly to the frequency of radiation $ω$. The system of Josephson junctions behaves like a single whole system: the Shapiro steps or their harmonics in the total IV-characteristics appear at voltage $\sum V_l=N_R\frac{m}{n}ω$, where $V_l$ is the voltage in $l$-th junction, $N_R$ is the number of JJ in the rotating state, and $m$ and $n$ are integer numbers.

cond-mat.supr-con↗
arXiv2012

Shapiro and parametric resonances in coupled Josephson junctions

The effect of microwave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We compare the current-voltage characteristics for a stack of coupled Josephson junctions under external irradiation calculated in the framework of CCJJ and CCJJ+DC models.

cond-mat.supr-con↗
arXiv2012

Variation of Longitudinal Plasma Wavelength under Irradiation and Double Resonance in Coupled Josephson Junctions

The effect of electromagnetic wave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We predict three novel effects by variation of the radiation amplitude and frequency: changing of the longitudinal plasma wavelength at parametric resonance; double resonance of the Josephson oscillations with radiation and longitudinal plasma wave; charging of superconducting layers in the current interval corresponding to the Shapiro step. The "bump" structure in IVC recently observed experimentally is demonstrated. We also observe ragged Shapiro steps at double resonance.

cond-mat.supr-con↗
arXiv2012

Manifestation of Resonance-Related Chaos in Coupled Josephson Junctions

Chaotic features of systems of coupled Josephson junctions are studied. Manifestation of chaos in the temporal dependence of the electric charge, related to a parametric resonance, is demonstrated through the calculation of the maximal Lyapunov exponent, phase-charge and charge-charge Lissajous diagrams and correlation functions. The number of junctions in the stack strongly influences the fine structure in the current voltage characteristics and a strong proximity effect results from the nonperiodic boundary conditions. The observed resonance-related chaos exhibits intermittency over a range of conditions and parameters. General features of the system are analyzed by means of a linearized equation and the criteria for a breakpoint region with no chaos are obtained. Such criteria could clarify recent experimental observations of variations in the power output from intrinsic Josephson junctions in high temperature superconductors.

cond-mat.supr-con↗
arXiv2011

Charging of Superconducting Layers and Novel Type of Hysteresis in Coupled Josephson Junctions

A manifestation of a novel type of hysteresis related to the parametric resonance in the system of coupled Josephson junctions is demonstrated. Opposite to McCumber and Steward hysteresis, we find that the width of this hysteresis is inversely proportional to the McCumber parameter and depends also on coupling between junctions and the boundary conditions. An investigation of time dependence of the electric charge in superconducting layers allow us to explain the origin of this hysteresis by different charge dynamics for increasing and decreasing bias current processes. The effect of wavelength of the longitudinal plasma waves created at the resonance on the charging of superconducting layers is demonstrated. We found a strong effect of the dissipation in the system on the amplitude of the charge oscillations at the resonance.

cond-mat.supr-con↗
arXiv2011

The c-axis charge traveling wave in coupled system of Josephson junctions

We demonstrate a manifestation of the charge traveling wave along the c-axis (TW) in current voltage characteristics of coupled Josephson junctions in high-$T_c$ superconductors. The branches related to the TW with different wavelengths are found for the stacks with different number of Josephson junctions at different values of system's parameters. Transitions between the TW branches and the outermost branch are observed. Time dependence of the electric charge in the superconducting layers and charge-charge correlation functions for TW and outermost branches show different behavior with bias current. We propose an experimental testing of the TW by microwave irradiation.

cond-mat.supr-con↗
arXiv2010

Charge creation and nucleation of longitudinal plasma wave in coupled Josephson junctions

We study the phase dynamics in coupled Josephson junctions describing by system of nonlinear differential equations. Results of detailed numerical simulations of charge creation in the superconducting layers and the longitudinal plasma wave (LPW) nucleation are presented. We demonstrate the different time stages in the development of the LPW and present results of FFT analysis at different values of bias current. The correspondence between the breakpoint position on the outermost branch of current voltage characteristics (CVC) and the growing region in time dependence of the electric charge in the superconducting layer is established. The effects of noise in the bias current and the external microwave radiation on the charge dynamics of the coupled Josephson junctions are found. These effects introduce a way to regulate the process of LPW nucleation in the stack of IJJ.

cond-mat.supr-con↗
arXiv2010

Study of charge-phase diagrams for coupled system of Josephson junctions

Dynamics of stacked intrinsic Josephson junctions (IJJ) in the high-Tc superconductors is theoretically investigated. We calculate the current-voltage characteristics (CVC) of IJJ and study the breakpoint region on the outermost branch of the CVC for the stacks with 9 IJJ. A method for investigation of the fine structure in CVC of IJJ based on the recording the "phase-charge" diagrams is suggested. It is demonstrated that this method reflects the main features of the breakpoint region.

cond-mat.mes-hall↗
arXiv2010

Influence of Josephson current second harmonic on stability of magnetic flux in long junctions

We study the long Josephson junction (LJJ) model which takes into account the second harmonic of the Fourier expansion of Josephson current. The dependence of the static magnetic flux distributions on parameters of the model are investigated numerically. Stability of the static solutions is checked by the sign of the smallest eigenvalue of the associated Sturm-Liouville problem. New solutions which do not exist in the traditional model, have been found. Investigation of the influence of second harmonic on the stability of magnetic flux distributions for main solutions is performed.

cond-mat.supr-con↗
arXiv2010

Numerical investigation of the second harmonic effects in the LJJ

We study the long Josephson junction (LJJ) model which takes into account the second harmonic of the Fourier expansion of Josephson current. The sign of second harmonic is important for many physical applications. The influence of the sign and value of the second harmonic on the magnetic flux distributions is investigated. At each step of numerical continuation in parameters of the model, the corresponding nonlinear boundary problem is solved on the basis of the continuous analog of Newton's method with the 4th order Numerov discretization scheme. New solutions which do not exist in the traditional model have been found. The influence of the second harmonic on stability of magnetic flux distributions for main solutions is investigated.

cond-mat.supr-con↗
arXiv2010

Numerical study of magnetic flux in the LJJ model with double sine-Gordon equation

The decrease of the barrier transparency in superconductor-insulator-superconductor (SIS) Josephson junctions leads to the deviations of the current-phase relation from the sinusoidal form. The sign of second harmonics is important for many applications, in particular in junctions with a more complex structure like SNINS or SFIFS, where N is a normal metal and F is a weak metallic ferromagnet. In our work we study the static magnetic flux distributions in long Josephson junctions taking into account the higher harmonics in the Fourier-decomposition of the Josephson current. Stability analysis is based on numerical solution of a spectral Sturm-Liouville problem formulated for each distribution. In this approach the nullification of the minimal eigenvalue of this problem indicates a bifurcation point in one of parameters. At each step of numerical continuation in parameters of the model, the corresponding nonlinear boundary problem is solved on the basis of the continuous analog of Newton's method. The solutions which do not exist in the traditional model have been found. The influence of second harmonic on stability of magnetic flux distributions for main solutions is investigated.

cond-mat.supr-con↗
arXiv2009

Effect of coupling between junctions on superconducting current and charge correlations in intrinsic Josephson junctions

Charge formations on superconducting layers and creation of the longitudinal plasma wave in the stack of intrinsic Josephson junctions change crucially the superconducting current through the stack. Investigation of the correlations of superconducting currents in neighboring Josephson junctions and the charge correlations in neighboring superconducting layers allows us to predict the additional features in the current--voltage characteristics. The charge autocorrelation functions clearly demonstrate the difference between harmonic and chaotic behavior in the breakpoint region. Use of the correlation functions gives us a powerful method for the analysis of the current--voltage characteristics of coupled Josephson junctions.

cond-mat.supr-con↗
arXiv2008

Experimental observation of the longitudinal plasma excitation in intrinsic Josephson junctions

We have investigated the current-voltage characteristics (IVCs) of intrinsic Josephson junctions (IJJs). Recently, it is predicted that the longitudinal plasma wave can be excited by the parametric resonance in IJJs. Such an excitation induces a singularity called as breakpoint region around switch back region in the IVC. We have succeeded in the observation of the breakpoint region in the IVC of the mesa with 5 IJJs at 4.2 K. Furthermore, it is found that the temperature dependence of the breakpoint current is in agreement with the theoretical prediction. This suggests that the wave number of the excited plasma wave varies with temperature.

cond-mat.supr-con↗
arXiv2008

Structure of the breakpoint region in CVC of the intrinsic Josephson junctions

A fine structure of the breakpoint region in the current-voltage characteristics of the coupled intrinsic Josephson junctions in the layered superconductors is found. We establish a correspondence between the features in the current-voltage characteristics and the character of the charge oscillations in superconducting layers in the stack and explain the origin of the breakpoint region structure.

cond-mat.supr-con↗