Yury Shukrinov

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.

Numerical study of fluxon solutions of sine-gordon equation under the influence of the boundary conditions

The dependence on the boundary conditions of the fluxon solutions of a boundary problem for the sine-Gordon equation (SGE) is investigated numerically. Interconnection between fluxon and constant solutions is analyzed. Numerical results are discussed in the context of the long Josephson junction model.

Experimental and theoretical investigation on high-Tc superconducting intrinsic Josephson junctions

Within the last years many groups have realized and investigated different types of intrinsic Josephson junction (IJJ) arrays out of high-temperature superconducting single crystals or thin films. We tried to improve the synchronization between the junctions by external shunts. Mesa structures as well as microbridges on vicinal cut substrates showed multi-branch behaviour in their IV characteristics and random switching between branches. Theoretical modelling was done investigating phase dynamics and stability numerically as well as analytically. Branch structure in current voltage characteristics of IJJ is studied in the framework of different models, particularly, in capacitevely coupled Josephson junctions (CCJJ) model and CCJJ model with diffusion current. Results of modelling of return current in IV characteristics for stacks with different number of IJJ are presented. We discussed the possible mechanisms of synchronization and the ranges of stability. Conclusions with respect to application of such arrays such as radiation sources were given.

Simulation of current voltage characteristics of intrinsic josephson junctions in HTSC

The current-voltage characteristics (CVC) of capacitively coupled Josephson junctions are numerically calculated. The methods of branch structure simulation in the CVC and charge dynamics of the coupled Josephson junctions are described in detail. We discuss the features of the parametric resonance and its manifestation in the CVC and in the charge-charge diagrams.

Shift of Shapiro Step in High Critical Temperature Superconductors

The influence of the charge imbalance effect on a system of intrinsic Josephson junctions of high temperature superconductors under external electromagnetic radiation is investigated. We find that the charge imbalance is responsible for the slope of the Shapiro step in the IV-characteristic. The nonperiodic boundary conditions shift the Shapiro step from the canonical position which is determined by the frequency of the external radiation. We also find how the system parameters influence the shift of the Shapiro step.