Negative Differential Resistance and Shapiro Steps in a Superconducting MoN Strip with a Cut

JETP Letters - Regions with a negative differential resistance have been revealed in the voltage–current characteristics of superconducting MoN strips with a side cut under high-power...     

Low-field peak effect in type II superconductors

The combined effect of a surface (edge) barrier and volume pinning on the dependence of critical current I _c on the magnetic field (I⊥H ₀) in bulk type II superconductors is investigated. In low magnetic fields, there is a portion of the curve I _c(H ₀) where I _c grows with H ₀, causing a nontrivial peak effect in this field range. Such behavior is explained by the combined effect of a surface (edge) barrier and volume pinning, the latter being rather sensitive to the transport current density distribution in a superconductor.     

Threshold perturbations in current-carrying superconducting bridges with a finite length near the critical temperature

Near the critical temperature of a superconducting transition, the energy of the threshold perturbation δF_thr that transfers a superconducting bridge to a resistive state at a current below the critical current I_c has been determined. It has been shown that δF_thr increases with a decrease in the length of a bridge for short bridges with lengths L < ξ (where ξ is the coherence length) and is saturated for long bridges with L ? ξ. At certain geometrical parameters of banks and bridge, the function δF_thr(L) at the current I → 0 has a minimum at L ~ (2–3)ξ. These results indicate that the effect of fluctuations on Josephson junctions made in the form of short superconducting bridges is reduced and that the effect of fluctuations on bridges with lengths ~(2–3)ξ is enhanced.     

Duality, triality and complementary extremum principles in non-convex parametric variational problems with applications

This paper presents a reasonably complete duality theory anda nonlinear dual transformation method for solving the fullynonlinear, non-convex parametric variational problem inf{W(u- µ) - F(u)}, and associated nonlinear boundary valueproblems, where is a nonlinear operator, W is either convexor concave functional of p = u, and µ is a given parameter.Detailed mathematical proofs are provided for the complementaryextremum principles proposed recently in finite deformationtheory. A method for obtaining truly dual variational principles(without a dual gap and involving the dual variable p* of uonly) in n-dimensional problems is proposed. It is proved thatfor convex W(p), the critical point of the associated LagrangianL_µ(u, p*) is a saddle point if and only if the so-calledcomplementary gap function is positive. In this case, the systemhas only one dual problem. However, if this gap function isnegative, the critical point of the Lagrangian is a so-calledsuper-critical point, which is equivalent to the Auchmuty'sanomalous critical point in geometrically linear systems. Wediscover that, in this case, the system may have more than oneprimal-dual set of problems. The critical point of the Lagrangianeither minimizes or maximizes both primal and dual problems.An interesting triality theorem in non-convex systems is proved,which contains a minimax complementary principle and a pairof minimum and maximum complementary principles. Applicationsin finite deformation theory are illustrated. An open problemleft by Hellinger and Reissner is solved completely and a purecomplementary energy principle is constructed. It is provedthat the dual Euler-Lagrange equation is an algebraic equation,and hence, a general analytic solution for non-convex variational-boundaryvalue problems is obtained. The connection between nonlineardifferential equations and algebraic geometry is revealed.     

Fast Discrete Fourier Transform on Local Fields of Zero Characteristic

For the discrete Fourier transform with respect to the system of characters of a local field with zero characteristic, we propose a fast algorithm. We find the complexity of the algorithm.     

Long-range nonlocal flow of vortices in narrow superconducting channels

We report a new nonlocal effect in vortex matter, where an electric current confined to a small region of a long and sufficiently narrow superconducting wire causes vortex flow at distances hundreds of intervortex separations away. The observed remote traffic of vortices is attributed to a very efficient transfer of a local strain through the one-dimensional vortex lattice (VL), even in the presence of disorder. We also observe mesoscopic fluctuations in the nonlocal vortex flow, which arise due to "traffic jams" when vortex arrangements do not match a local geometry of a superconducting channel.     

Current-voltage characteristics of quasi-one-dimensional superconductors: an S-shaped curve in the constant voltage regime

Applying a constant voltage to superconducting nanowires we find that its I-V characteristic exhibits an unusual S behavior. This behavior is the direct consequence of the dynamics of the superconducting condensate and of the existence of two different critical currents: j(c2) at which the pure superconducting state becomes unstable and j(c1)相似文献   

Peculiarities of the Nonlinear Response of a Superconductor–Normal Metal Structure with a Large Ratio of Resistivities

Physics of the Solid State - Using the near-field microwave microscopy method, the temperature dependence of third harmonics power P3ω(T) of the MoN/Al superconductor–normal metal...     

Dynamics of Domain Walls in a Fulde–Ferrell Superconductor

JETP Letters - The mechanism of switching between different states of a quasi-one-dimensional current-carrying superconductor in the Fulde–Ferrell phase has been theoretically studied. It has...     

Stable and metastable states in a mesoscopic superconducting “eight” loop in presence of an external magnetic field

The stable and metastable states of different configurations of a mesoscopic loop in the form of an eight is studied in the presence of a magnetic field. We find that for certain configurations the current is equal to zero for any value of the magnetic field leading to a magnetic field independent superconducting state. The state with fixed phase circulation becomes unstable when the momentum of the superconducting electrons reaches a critical value. At this moment the kinetic energy of the superconducting condensate becomes of the same order as the potential energy of the Cooper pairs and it leads to an instability. Numerical analysis of the time-dependent Ginzburg–Landau equations shows that the absolute value of the order parameter changes gradually at the transition from a state with one phase circulation to another although the vorticity change occurs abruptly.