Search results for "conductivity"
showing 10 items of 1988 documents
Generalization of Blonder-Tinkham-Klapwijk theory to particle-hole mixing boundary conditions: \pi-shift and conductance dips
2015
We generalize the Blonder-Tinkham-Klapwijk theory considering non-diagonal boundary conditions in the Bogoliubov-de Gennes scattering problem, to describe anomalous conductance features often reported for normal-metal/superconductor contacts. We calculate the differential conductance spectra showing that conductance dips, not expected in the standard formulation, are explained in terms of phase \pi-shift, between the bulk and the interface order parameter, possibly induced by a localized magnetic moment. A discretized model is used to give quantitative evaluation of the physical conditions, namely the polarization and transparency of the interface, needed to realize the phase gradient.
c-Axis tunneling in YBa2Cu3O7-\delta/PrBa2Cu3O7-\delta superlattices
2000
In this work we report c-axis conductance measurements done on a superlattice based on a stack of 2 layers YBa2Cu3O{7-\delta} and 7 layers PrBa2Cu3O{7-\delta} (2:7). We find that these quasi-2D structures show no clear superconducting coupling along the c-axis. Instead, we observe tunneling with a gap of \Delta_c=5.0\pm 0.5 meV for the direction perpendicular to the superconducting planes. The conductance spectrum show well defined quasi-periodic structures which are attributed to the superlattice structure. From this data we deduce a low temperature c-axis coherence length of \xi_c=0.24\pm 0.03 nm.
Resistive State of Superconductor-Ferromagnet-Superconductor Josephson Junctions in the Presence of Moving Domain Walls
2019
We describe resistive states of the system combining two types of orderings—a superconducting and a ferromagnetic one. It is shown that in the presence of magnetization dynamics such systems become inherently dissipative and in principle cannot sustain any amount of the superconducting current because of the voltage generated by the magnetization dynamics. We calculate generic current-voltage characteristics of a superconductor-ferromagnet-superconductor Josephson junction with an unpinned domain wall and find the low-current resistance associated with the domain wall motion. We suggest the finite slope of Shapiro steps as the characteristic feature of the regime with domain wall oscillatio…
"Table 1" of "A Precise Determination of the Number of Families With Light Neutrinos and of the $Z$ Boson Partial Widths"
1990
Penetrating charged particle track selection.
Nanosecond voltage pulses from dendritic flux avalanches in superconducting NbN films
2013
Combined voltage and magneto-optical study of magnetic flux flow in superconducting NbN films is reported. The nanosecond-scale voltage pulses appearing during thermomagnetic avalanches have been recorded in films partially coated by a metal layer. Simultaneous magneto-optical imaging and voltage measurements allowed the pulses to be associated with individual flux branches penetrating the superconductor below the metal coating. From detailed characteristics of pulse and flux branches, the electrical field in the superconductor is found to be in the range of 5-50 kV/m, while the propagation speed of the avalanche during its final stage is found to be close to 5 km/s. peerReviewed
Pac-Man Josephson junctions: useful trigonometric puzzles?
2021
Abstract Rather interesting trigonometric equations arise when considering a Josephson junction obtained by embedding a Pac-Man shaped superconducting island in between two superconducting electrodes. In the present work we unfold these equations, written in terms of the superconducting phase difference between the two electrodes, and find the current-phase relation and the maximum superconducting current of the Josephson junction network. The solution of the trigonometric equations defining the superconducting current state of the system can be proposed to advanced high-school students or to undergraduate students in an interdisciplinary lecture.
Локальные и интегральные свойства квазиодномерного сверхпроводника в режиме квантовых флуктуаций параметра порядка
2021
Utilization of superconducting materials for the new generation of nanoelectronic devices seems extremely tempting from the point of view of the absence of Joule heating. However, in small systems, the role of fluctuations can be very significant. In this work, the transport properties of thin superconducting titanium nanostructures were studied experimentally and theoretically. It has been shown that quantum fluctuations of the order parameter have a dif-ferent impact on integral and local characteristics of a quasi-one-dimensional superconductor. In sufficiently thin nanowires, a finite electrical resistance can be observed at the lowest tem-peratures, while the tunneling current-voltage…
Сверхпроводящие микроструктуры с высоким импедансом
2020
Abstract The transport properties of two types of quasi-one-dimensional superconducting microstructures were investigated at ultra-low temperatures: the narrow channels close-packed in the shape of meander, and the chains of tunneling contacts “superconductor-insulator-superconductor.” Both types of the microstructures demonstrated high value of high-frequency impedance and-or the dynamic resistance. The study opens up potential for using of such structures as current stabilizing elements with zero dissipation.
Change of the vortex core structure in two-band superconductors at the impurity-scattering-driven s±/s++ crossover
2017
We report a nontrivial transition in the core structure of vortices in two-band superconductors as a function of interband impurity scattering. We demonstrate that, in addition to singular zeros of the order parameter, the vortices there can acquire a circular nodal line around the singular point in one of the superconducting components. It results in the formation of the peculiar “moat”-like profile in one of the superconducting gaps. The moat-core vortices occur generically in the vicinity of the impurity-induced crossover between s± and s++ states. peerReviewed
Phase diagram of dirty two-band superconductors and observability of impurity-induced s + i s state
2017
We investigate the phase diagram of dirty two-band superconductors. This paper primarily focuses on the properties and observability of the time-reversal symmetry-breaking s + is superconducting states, which can be generated in two-band superconductors by interband impurity scattering. We show that such states can appear in two distinct ways. First, according to a previously discussed scenario, the s + is state can form as an intermediate phase at the impurity-driven crossover between s± and s++ states. We show that there is a second scenario where domains of the s + is state exists in the form of an isolated dome inside the s± domain, completely detached from the transition between s± and…