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R. G. Mints

Publications and source records attributed to R. G. Mints.

32 records · Page 2Linked to original sources
arXiv2004

Flux creep in type-II superconductors: self-organized criticality approach

We consider the current density distribution function of a flux creep regime in type-II superconductors by mapping the flux creep process to the dynamics of a model with a self-organized criticality. We use an extremal Robin Hood type model which evolves to Been's type critical state to treat magnetic flux penetration into a superconductor and derive an analog of the current-voltage characteristics in the flux creep region.

cond-mat.supr-con↗
arXiv2004

On ultrafast magnetic flux dendrite propagation into thin superconducting films

We suggest a new theoretical approach describing the velocity of magnetic flux dendrite penetration into thin superconducting films. The key assumptions for this approach are based upon experimental observations. We treat a dendrite tip motion as a propagating flux jump instability. Two different regimes of dendrite propagation are found. A fast initial stage is followed by a slow stage, which sets in as soon as a dendrite enters into the vortex-free region. We find that the dendrite velocity is inversely proportional to the sample thickness. The theoretical results and experimental data obtained by a magneto-optic pump-probe technique are compared and excellent agreement between the calculations and measurements is found.

cond-mat.supr-con↗
arXiv2003

Properties of mesoscopic superconducting thin-film rings. London approach

Superconducting thin-film rings smaller than the film penetration depth (the Pearl length) are considered. The current distribution, magnetic moment, and thermodynamic potential ${\cal F}(H,N,v)$ for a flat, washer-shaped annular ring in a uniform applied field $H$ perpendicular to the film are solved analytically within the London approach for a state with winding number $N$ and a vortex at radius $v$ between the inner and outer radii.

cond-mat.supr-con↗
arXiv2001

Fractional Josephson vortices at YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

We report numerical simulations of magnetic flux patterns in asymmetric 45$^{\circ}$ [001]-tilt grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films. The grain boundaries are treated as Josephson junctions with the critical current density $j_c(x)$ alternating along the junctions. We demonstrate the existence of Josephson vortices with fractional flux quanta for both periodic and random $j_c(x)$. A method is proposed to extract fractional vortices from experimental flux patterns.

cond-mat.supr-con↗
arXiv2000

Self-generated magnetic flux in YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

Grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films are considered as Josephson junctions with a critical current density $j_c(x)$ alternating along the junction. A self-generated magnetic flux is treated both analytically and numerically for an almost periodic distribution of $j_c(x)$. We obtained a magnetic flux-pattern similar to the one which was recently observed experimentally.

cond-mat.supr-con↗
arXiv1999

Buckling instability in type-II superconductors with strong pinning

We predict a novel buckling instability in the critical state of thin type-II superconductors with strong pinning. This elastic instability appears in high perpendicular magnetic fields and may cause an almost periodic series of flux jumps visible in the magnetization curve. As an illustration we apply the obtained criteria to a long rectangular strip.

cond-mat.supr-con↗
arXiv1997

Proximity Effect Enhancement Induced by Roughness of SN Interface

Critical temperature reduction $ΔT_c$ is considered for a thin film of a layered superconductor (S) with a rough surface covered by a thick layer of a normal metal (N). The roughness of the SN interface increases the penetration of electrons from the normal metal into the superconductor and leads to an enhancement of the proximity effect. The value of $ΔT_c$ induced by the roughness of the SN interface can be much higher than $ΔT_c$ for a film with a plain surface for an extremely anisotropic layered superconductor with the coherence lengths $ξ_a,ξ_b\ggξ_c$.

cond-mat.supr-con↗
arXiv1995

Long-Range Fluctuation-Induced Attraction of Vortices to the Surface in Layered Superconductors

It is shown that in extremely anisotropic layered superconductors the interaction of vortex lines with a parallel planar surface, which for straight lines along the c-axis decreases exponentially over the in-plane penetration depth $λ$, becomes a long-range dipole--dipole attraction when the vortex line is distorted randomly. This novel long-range fluctuation-induced attraction enhances the thermal fluctuations down to depths much larger than $λ$ and may lead to flux creep towards the surface.

cond-mat↗
arXiv1995

Flux Creep and Flux Jumping

We consider the flux jump instability of the Bean's critical state arising in the flux creep regime in type-II superconductors. We find the flux jump field, $B_j$, that determines the superconducting state stability criterion. We calculate the dependence of $B_j$ on the external magnetic field ramp rate, $\dot B_e$. We demonstrate that under the conditions typical for most of the magnetization experiments the slope of the current-voltage curve in the flux creep regime determines the stability of the Bean's critical state, {\it i.e.}, the value of $B_j$. We show that a flux jump can be preceded by the magneto-thermal oscillations and find the frequency of these oscillations as a function of $\dot B_e$.

supr-con↗
arXiv1995

Self-Organized Criticality Effect on Stability: Magneto-Thermal Oscillations in a Granular YBCO Superconductor

We show that the self-organized criticality of the Bean's state in each of the grains of a granular superconductor results in magneto-thermal oscillations preceding a series of subsequent flux jumps. We find that the frequency of these oscillations is proportional to the external magnetic field sweep rate and is inversely proportional to the square root of the heat capacity. We demonstrate experimentally and theoretically the universality of this dependence that is mainly influenced by the granularity of the superconductor.

supr-con↗
arXiv1994

Electromagnetic waves in a Josephson junction in a thin film

We consider a one-dimensional Josephson junction in a superconducting film with the thickness that is much less than the London penetration depth. We treat an electromagnetic wave propagating along this tunnel contact. We show that the electrodynamics of a Josephson junction in a thin film is nonlocal if the wave length is less than the Pearl penetration depth. We find the integro-differential equation determining the phase difference between the two superconductors forming the tunnel contact. We use this equation to calculate the dispersion relation for an electromagnetic wave propagating along the Josephson junction. We find that the frequency of this wave is proportional to the square root of the wave vector if the wave length is less than the Pearl penetration depth.

cond-mat↗
arXiv1994

Josephson Vortex Bloch Oscillations: Single Pair Tunneling Effect

We consider the Josephson vortex motion in a long one--dimensional Josephson junction in a thin film. We show that this Josephson vortex is similar to a mesoscopic capacitor. We demonstrate that a single Cooper pair tunneling results in nonlinear Bloch--type oscillations of a Josephson vortex in a current-biased Josephson junction. We find the frequency and the amplitude of this motion.

cond-mat↗
arXiv1994

Josephson vortex Cherenkov radiation

We predict the Josephson vortex Cherenkov radiation of an electromagnetic wave. We treat a long one--dimensional Josephson junction. We consider the wave length of the radiated electromagnetic wave to be much less than the Josephson penetration depth. We use for calculations the nonlocal Josephson electrodynamics. We find the expression for the radiated power and for the radiation friction force acting on a Josephson vortex and arising due to the Cherenkov radiation. We calculate the relation between the density of the bias current and the Josephson vortex velocity.

cond-mat↗