Nonequilibrium statistical operators for systems with finite lifetime

A family of nonequilibrium statistical operators (NSO) is introduced which differ by the system lifetime distribution over which the quasiequilibrium (relevant) distribution is averaged. This changes the form of the source in the Liouville equation, as well as the expressions for the kinetic coefficients, average fluxes, and kinetic equations obtained with use of NSO. The difference from the Zubarev form of NSO is of the order of the reciprocal lifetime of a system

Planar SFS Josephson Junctions Made by Focused Ion Beam Etching

Superconductor-Ferromagnet-Superconductor (S-F-S) Josephson junctions were fabricated by making a narrow cut through a S-F double layer using direct writing by Focused Ion Beam (FIB). Due to a high resolution (spot size smaller than 10 nm) of FIB, junctions with a small separation between superconducting electrodes ($\leq$ 30 nm) can be made. Such a short distance is sufficient for achieving a considerable proximity coupling through a diluted CuNi ferromagnet. We have successfully fabricated and studied S-F-S (Nb-CuNi-Nb) and S-S'-S (Nb-Nb/CuNi-Nb) junctions. Junctions exhibit clear Fraunhofer modulation of the critical current as a function of magnetic field, indicating good uniformity of the cut. By changing the depth of the cut, junctions with the $I_c R_n$ product ranging from 0.5 mV to $\sim 1\mu$V were fabricated.Comment: 5 pages, 5 figures, presentation at EUCAS-2003, to be published in Physica

Lifetime distributions in the methods of non-equilibrium statistical operator and superstatistics

A family of non-equilibrium statistical operators is introduced which differ by the system age distribution over which the quasi-equilibrium (relevant) distribution is averaged. To describe the nonequilibrium states of a system we introduce a new thermodynamic parameter - the lifetime of a system. Superstatistics, introduced in works of Beck and Cohen [Physica A \textbf{322}, (2003), 267] as fluctuating quantities of intensive thermodynamical parameters, are obtained from the statistical distribution of lifetime (random time to the system degeneracy) considered as a thermodynamical parameter. It is suggested to set the mixing distribution of the fluctuating parameter in the superstatistics theory in the form of the piecewise continuous functions. The distribution of lifetime in such systems has different form on the different stages of evolution of the system. The account of the past stages of the evolution of a system can have a substantial impact on the non-equilibrium behaviour of the system in a present time moment.Comment: 18 page

General Beltrami equations and BMO

We study the Beltrami equations ∂f = μ(z)∂f + ν(z)∂f under the assumption that the coefficients μ, ν satisfy the inequality |μ| + |ν| < 1 almost everywhere. Sufficient conditions for the existence of homeomorphic ACL solutions to the Beltrami equations are given in terms of the bounded mean oscillation by John and Nirenberg

Пельвиометрия с помощью приминения ядерно-магнитного резонанса при субклинических формах узкого таза и определения риска в случае дистоции пречиков

Military Medical Academy, Department of radiology, St-Petersburg, Russia, Federal Center of blood, heart and endocrinology by VA. Almazov, St-Petersburg, RussiaВо многих странах точность измерений размеров наружного таза сомнительна. Распространенность подтипов субклинически узкого костного таза еще более затрудняет диагностику. Цель: установить акушерские МР пельвиометрические и фетометрические референсные значения при оценке риска дистоции плечиков плода перед родами и сравнить МР пельвиометрию с наружными методами измерения. Методы: обследованы 40 женщин с одноплодной беремонностью в сроке 38-39 недель. МР пепьвиометрия производилась на высокопольном 1,5 Т MRT. Все субклинические типы узкого костного таза были разделены на 3 степени. Проводилась также фетометрия. Риск дистоции определялся как минимальный, возможный и высокий. Результаты: Абсолютно узкий таз был выявлен у 3 женщин. Диаметр костного таза, измеренный на МРТ, был нормальным у 14 (35%) женщин. Двенадцати женщинам (30%) со 2 степенью узкого таза и/или крупным плодом (>4000 г) при отсутствии других противопоказаний было рекомендовано родоразрешение через естественные родовые пути, но 6 из них выполнено КС. Заключение: низкая частота выявления субклинически узкого костного таза при наружных измерениях может приводить к запоздалой интранатальной диагностики этой патологии. МР пельвиометрия выявляла субклиническое сужение костного таза. Дополнительные данные фетометрии помогли оценить риск дистоции плечиков перед родами

Andreev conductance of a domain wall

At low temperatures, the transport through a superconductor-ferromagnet tunnel interface is due to tunneling of electrons in pairs. Exchange field of a monodomain ferromagnet aligns electron spins and suppresses the two electron tunneling. The presence of the domain walls at the SF interface strongly enhances the subgap current. The Andreev conductance is proven to be proportional to the total length of domain walls at the SF interface.Comment: 4 pages and 1 figur

Magnetization Dynamics in Proximity-Coupled Superconductor-Ferromagnet-Superconductor Multilayers:II. Thickness Dependence of the Superconducting Torque

In this work, we study magnetization dynamics in superconductor-ferromagnet-superconductor thin-film structures. Results of the broad-band ferromagnetic resonance spectroscopy are reported for a large set of samples with varied thickness of both superconducting and ferromagnetic layers in a wide frequency, field, and temperature ranges. Experimentally the one-dimensional anisotropic action of superconducting torque on magnetization dynamics is established; its dependence on thickness of layers is revealed. It is demonstrated that experimental findings support the recently proposed mechanism of the superconducting torque formation via the interplay between the superconducting imaginary conductance and magnetization precession at superconductor-ferromagnet interfaces. Microwave spectroscopy studies in this work are supplemented by investigations of the crystal structure and the microstructure of studied multilayers.</p

Inhomogeneous magnetism induced in a superconductor at superconductor-ferromagnet interface

We study a magnetic proximity effect at superconductor (S) - ferromagnet (F) interface. It is shown that due to an exchange of electrons between the F and S metals ferromagnetic correlations extend into the superconductor, being dependent on interface parameters. We show that ferromagnetic exchange field pair breaking effect leads to a formation of subgap bands in the S layer local density of states, that accommodate only one spin-polarized quasiparticles. Equilibrium magnetization leakage into the S layer as function of SF interface quality and a value of ferromagnetic interaction have also been calculated. We show that a damped-oscillatory behavior versus distance from SF interface is a distinguished feature of the exchange-induced magnetization of the S layer.Comment: 10 pages, 7 Postscript figure

Periodic alternating 0,π0,\pi-junction structures as realization of ϕ\phi-Josephson junctions

We consider the properties of a periodic structure consisting of small alternating 0- and pi- Josephson junctions. We show that depending on the relation between the lengths of the individual junctions, this system can be either in the homogeneous or in the phase-modulated state. The modulated phase appears via a second order phase transition when the mismatch between the lengths of the individual junctions exceeds the critical value. The screening length diverges at the transition point. In the modulated state, the equilibrium phase difference in the structure can take any value from -pi to pi (phi-junction). The current-phase relation in this structure has very unusual shape with two maxima. As a consequence, the field dependence of the critical current in a small structure is very different from the standard Fraunhofer dependence. The Josephson vortex in a long structure carries partial magnetic flux, which is determined by the equilibrium phase.Comment: 4 pages, 3 figues, submitted to Phys. Rev.

Minigap in a long disordered SNS junction: analytical results

We review and refine analytical results on the density of states in a long disordered superconductor - normal-metal - superconductor junction with transparent interfaces. Our analysis includes the behavior of the minigap near phase differences zero and PI across the junction, as well as the density of states at energies much larger than the minigap but much smaller than the superconducting gap.Comment: 4 page