Influence of Film Thickness on D. C. Josephson Current

Weihnacht, M.

doi:10.1002/pssb.19690320259

Cited by 78 publications

(47 citation statements)

References 5 publications

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“…1a). From the experimental magnetic field period HE40 Oe, we get t H E57 nm in good agreement with 59 nm obtained from geometrical considerations 19 . We note that lateral dimensions of the JJs are much smaller than the Josephson penetration depth, l J ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi pF 0 LW=m 0 I c;0 t H p B1 mm, therefore providing the frame of the short junction limit 18 .…”

Section: Resultssupporting

confidence: 86%

A quantum diffractor for thermal flux

2014

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Macroscopic phase coherence between weakly coupled superconductors leads to peculiar interference phenomena. Among these, magnetic flux-driven diffraction might be produced, in full analogy to light diffraction through a rectangular slit. This can be experimentally revealed by the electric current and, notably, also by the heat current transmitted through the circuit. The former was observed more than 50 years ago and represented the first experimental evidence of the phase-coherent nature of the Josephson effect, whereas the second one was still lacking. Here we demonstrate the existence of heat diffraction by measuring the modulation of the electronic temperature of a small metallic electrode nearbycontacted to a thermally biased short Josephson junction subjected to an in-plane magnetic field. The observed temperature dependence exhibits symmetry under magnetic flux reversal, and clear resemblance with a Fraunhofer-like modulation pattern. Our approach, joined to widespread methods for phase-biasing superconducting circuits, might represent an effective tool for controlling the thermal flux in nanoscale devices.

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Section: Resultssupporting

confidence: 86%

A quantum diffractor for thermal flux

2014

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“…At small L/1, g = L/lJ holds. At L/AJ = 6 the value y = 2 is reached and instead of (9) equation (8) can be used.…”

Section: Discussion Of the Theoretical Relationsmentioning

confidence: 99%

The critical current of miniature thin film Josephson junctions with high current densities

Dettmann

Weber

1980

Phys. Stat. Sol. (a)

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Nb-Nb0,-Pb tunnel junctions with areas of about 10 x 10 pm2 and high current densities are prepared by cleaning the niobium surface in a rf glow discharge. The dependence of the critical Josephson currents on magnetic field is investigated. To a first approximation the behaviour of the critical current is described by the theory of one-dimensional junctions. Critical current densities up t~ 2 x 105 A/cma are reached. Nb-NbO,-Pb-Tiinnelverbindui~genmit Fliichen von etwe 10 X 10 ym2 und mit hohen Strorndichten werden durch Reinigen der Nioboberflache in einer HF-Glimmentladung hergestellt. Die Abhingigkeit des kritischen Josephsonstromes vom Magnetfeld wird untersucht. In erster Niiherung wird das Verhalten des kritischen Stromes durch die Theorie fur eindimensionale Tunnelverbindungen beschrieben. Es werden kritische Stromdichten bis zii 2 x 105 A/cm2 erreicht. F. DETTMAXN and P. B. WEBER where y is the phase difference between the two superconductors and [8 to 101is the Josephson penetrat*ion depth, 4 and 1, are the London penetration depths, dl and d, the thicknesses of the electrode films, t is the thickness of the barrier, jo the maximum current density, Go the flux quantum, and pcco the free space permeability. The current density in bhe barrier is given by

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“…vs H should follow a Fraunhofer pattern, l, (H) =1, (0)~sin(x)/x~, with x =zoo(2A+t)wH/@o. w is the junction width perpendicular to H, t is the barrier thickness, and k is the magnetic penetration depth. In BSCCO the factor (2A, +t ) has to be replaced by the distance between the midpoints of the electrodes [7,9], approximately 15 A in BSCCO. Therefore the field scale of the I, .…”

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“…The contact resistivities were typi- For the magnetic field measurements the crystals were oriented by a two-axis goniometer. The microwave absorption experiments (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) were performed in Cu cavities. For the emission experiments the crystals were mounted inside a horn at the end of an X-band waveguide.…”

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confidence: 99%

Intrinsic Josephson effects inBi2Sr2
Kleiner¹,
Steinmeyer²,
Kunkel³
et al. 1992
Phys. Rev. Lett.

1,246

562

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We have observed Josephson coupling between CuO double layers in Bi2Sr2CaCu20& single crystals by direct measurements of ac and dc Josephson effects with current flow along the r axis. The results show that a small Bi2Sr2CaCu20& single crystal behaves like a series array of Josephson junctions which can exhibit mutual phase locking.PACS numbers: 74.50.+r, 74.60.Jg, 74.70.jm The theory of layered oxide superconductors focuses on the possible types of coupling within the essential structure elements: the CuO planes. Ho~ever, independent of the exact nature of the pairing mechanism within the layers, the t'nterlayer coupling determines most of the superconducting properties of a real crystal. To date it is not clear how the Cooper pairs move across the interlayer spacing. In Bi2Sr2CaCu20s (BSCCO) the upper critical magnetic fields are so large that the standard anisotropic Ginzburg-Landau theory yields c-axis coherence lengths g, of the order of I A [I]. This is much less than the distance of 12 A between the CuO double layers. Therefore, the Lawrence-Doniach picture would be more appropriate [2], i.e., BSCCO should be described as a set of discrete superconducting layers whose order parameters are coupled by Josephson interaction. Several theories [2,3] and recent experiments concerning the angle dependence of the critical current [4] and the torque [5] support this idea. A convincing proof, however, can only be given by direct measurements of ac and dc Josephson efl'ects [5]. The simplest model of a BSCCO superconductor is a stack of superconducting sheets consisting of the CuO bilayers separated by the BiO and SrO layers acting as weak links or as insulators. Experimentally we therefore have to consider series arrays of proximity [superconductor-normal-metal-superconductor (SNS)] or tunneling [semiconductor-insulator-semiconductor (SIS)] Josephson junctions and pay attention to the following points.(I) If the c-axis supercurrents are limited by the Josephson effect, the I-V characteristics exhibit a concave curvature in the resistive state. If, on the other hand, the supercurrents are limited by flux flow, this curvature is convex. Therefore the I-V characteristics give first-hand information whether or not the supercurrents are of the Josephson type.(2) If the (ab)-plane dimensions of the Josephson junctions are larger than the Josephson penetration length A, j, Josephson vortices can be formed in the barrier. Whereas in standard tunnel junctions k~i s governed by the magnetic self-fields of the Josephson currents, in BSCCO kj is dominated by the kinetic momentum of the current flow along the (ab) axes, because the thickness of the electrodes (i.e., the CuO double layers) is much smaller than the field penetration depth along the e axis (A. ,q = 3000 A) [6]. The Lawrence-Doniach theory yields A, j=yt, where t is the interlayer spacing and y is the penetration depth anisotropy ratio [7]. For BSCCO k, = 100 pm [8], which yields X~= 0.4 pm.(3) In standard tunnel junctions with an electrode thickness larger than ...

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Influence of Film Thickness on D. C. Josephson Current

Cited by 78 publications

References 5 publications

A quantum diffractor for thermal flux

A quantum diffractor for thermal flux

The critical current of miniature thin film Josephson junctions with high current densities

Intrinsic Josephson effects inBi2Sr2
Kleiner¹,
Steinmeyer²,
Kunkel³
et al. 1992
Phys. Rev. Lett.

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Influence of Film Thickness on D. C. Josephson Current

Cited by 78 publications

References 5 publications

A quantum diffractor for thermal flux

A quantum diffractor for thermal flux

The critical current of miniature thin film Josephson junctions with high current densities

Intrinsic Josephson effects inBi2Sr2Kleiner1, Steinmeyer2, Kunkel3 et al. 1992Phys. Rev. Lett.

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Intrinsic Josephson effects inBi2Sr2
Kleiner¹,
Steinmeyer²,
Kunkel³
et al. 1992
Phys. Rev. Lett.