Critical josephson currents of evaporated NbNbOxPb tunnel junctions

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The properties of VNb–NbOx–Pb and NbV–VOx–Pb Josephson tunnel junctions are investigated. The behaviour of the VNb–NbOx–Pb junctions is as expected for tunnels with proximity effect. The junctions with the VOx barriers have anomalous small critical currents and very large excess currents. Both, the temperature dependence of the critical current and the excess current of these junctions deviate strongly from that of other known tunnel junctions. The interaction of the tunneling electrons with strong internal magnetic fields within the VOx is discussed as a possible reason of these deviations.

Section: Preparation Of the Junctions And Experimental Techniquesmentioning

confidence: 99%

The influence of vanadium oxide on the properties of Josephson tunnel junctions

Dettmann

Albrecht

1979

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“…This overheating increases with decreasing heat transniission coefficient, which changes discontinuously a t the phase transition points of heliuni. Because of the very good BCS behaviour of S b in the case of small current density [4] the difference between nieaswed and BCS curve in Fig. 1 is directly the overheating ternperature.…”

Section: Temperature Dependence Of the Gap Voltagementioning

confidence: 92%

“…2 [ 5 ] . For this case of nmcroscopic inhoniogeneity [4] p sinh (p) cos (aq) + qa cosh (/I) is the ratio of the critical current densities in the niidtlle and a t the edge of the tunnel area. Fig.…”

Section: Distribution Of the Current Dejssity In The Tunnel Areamentioning

confidence: 99%

Some properties of miniature NbNbOxPb tunnel junctions

Kohler

Blüthner

Linke

et al. 1978

NbNbOxPb tunnel junctions with minimum dimensions of 10 × 10 μm2 are investigated for determining the gap voltage in the temperature range 1.8 to 9 K. The experimental gap values are compared with values, which are calculated from the BCS theory. The deviations are explained with dissipative processes. Moreover the distribution of the current density within the tunnel area for one representative tunnel junction is determined with the Ic(Φ)‐curve on the base of new theoretical equations.

A study of VVOxPb Josephson tunnel junctions

Dettmann

Blüthner

Pertsch

et al. 1977

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The current-voltage characteristics and especially the behaviour of the critical Josephson currents of V-V0,-Pb tunnel junctions are investigated experimentally. The maximum Josephson current and its temperature dependence deviate strongly from the theory. The London penetration depth of the vanadium films is found to be much larger than for pure vanadium but its temperature dependence is as expected from theory. The critical temperatures of the vanadium films are between 4.4 and 5.0 K. The ratio 2A(0)/(kFc) decreases with decreasing critical temperature as in the case of superconductors with paramagnetic impurities. The excess currents in the current-voltage characteristics of the tunnel junctions at low voltages are not related to the critical temperatures of the vanadium films. Die Strom-Spannungs-Kennlinien und besonders das Verhalten des kritischen Josephsonstromes von V-V0,-Pb-Tunnelverbindungen werden experimentell untersucht. Der maximale Josephsonstrom und seine TempcraturabhLngigkeit weichen stark von der Theorie ab. Die Londonsche Eindringtiefe der Vanadinschichten ist wesentlich groBer als die fur reines Vanadin, ihre Temperaturabhiingigkeit stimmt jedoch mit der Theorie uberein. Die kritischen Temperaturen der Vanadinschichten liegen zwischen 4,4 und 6,O K. Das Verhaltnis 2A(O)/(kT,) fallt mit abnehmender kritischer Temperatur, wie es fur den Fall eines Supraleiters mit paramagnetischen Verunreinigungen erwartet wid. Die GroBe der VberschuBstrome in den Strom-Spannungs-Kennlinien der Tunnelverbindungen bei geringen Spannungen hangt nicht systematisch von der kritischen Temperatur der Vanadinschichten ab.