Influence of the passive region on zero field steps for window Josephson junctions

To study how nonlinear waves propagate across Y- and T-type junctions, we consider the two-dimensional (2D) sine-Gordon equation as a model and examine the crossing of kinks and breathers. Comparing energies for different geometries reveals that, for small widths, the angle of the fork plays no role. Motivated by this, we introduce a one-dimensional effective model whose solutions agree well with the 2D simulations for kink and breather solutions. These exhibit two different behaviors: a kink crosses if it has sufficient energy; conversely a breather crosses when v>1-ω, where v and ω are, respectively, its velocity and frequency. This methodology can be generalized to more complex nonlinear wave models.

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“…Note however that for small amplitudes, i.e. in the linear limit ω 1 = ω 2 so that we recover (14) for the critical velocity.…”

Section: A 1d Effective Modelmentioning

confidence: 69%

Nonlinear waves in networks: Model reduction for the sine-Gordon equation

Caputo

Dutykh

2014

Phys. Rev. E

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“…Numerically This turns out to be a universal feature which has been exhibited in numerical simulations of symmetric Nb-AlO x -Nb junctions [56]. We could not explain these discrepancies within the present model and can attribute those to a possible influence of the idle region [65][66][67][68][69][70][71][72][73] which we neglect in the present model. The discrepancy for even higher voltages above 1.5 mV is associated with the influence of non-equilibrium effects which were also observed in Ref.…”

Section: Numerical Calculation Of Ivc Of Nb-aln-nbn Ffomentioning

confidence: 70%

Microscopic Tunneling Model of Nb–AlN–NbN Josephson Flux-Flow Oscillator

2018

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Since the very first experimental realization of Josephson flux-flow oscillator (FFO), its theoretical description has been limited by the phenomenological perturbed sine-Gordon equation (PSGE). While PSGE can qualitatively describe the topological excitations in Josephson junctions that are sine-Gordon solitons or fluxons, it is unable to capture essential physical phenomena of a realistic system such as the coupling between tunnel currents and electromagnetic radiation. Furthermore, PSGE neglects any dependence on energy gaps of superconductors and makes no distinction between symmetric and asymmetric junctions: those made of two identical or two different superconducting materials. It was not until recently when it became possible to calculate properties of FFO by taking into account information about energy gaps of superconductors [D. R. Gulevich et al., Phys. Rev. B 96, 024215 (2017)]. Such approach is based on the microscopic tunneling theory and has been shown to describe essential features of symmetric Nb-AlOx-Nb junctions.Here we extend this approach to asymmetric Nb-AlN-NbN junctions and compare the calculated current-voltage characteristics to our experimental results.

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“…A possible explanation could be the influence of the idle region [110][111][112][113][114][115][116][117][118] which may have a stabilizing effect on the dynamics of FFO and, presumably, affect the values of MFFCs. Influence of the idle region on the dynamics of FFO has been neglected in our theoretical treatment (except for the renormalization of Josephson penetration length on which it has an effect [115,116]).…”

Section: Comparison To Experimental Resultsmentioning

confidence: 99%

Josephson flux-flow oscillator: The microscopic tunneling approach

2017

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Citation: GULEVICH, D.R., KOSHELETS, V.P. and KUSMARTSEV, F.V., 2017.Josephson flux-flow oscillator:The microscopic tunneling approach.Physical Review B, 96 (2), 024515-1 -024515-12.Additional Information:• We elaborate a theoretical description of large Josephson junctions which is based on Werthamer's microscopic tunneling theory. The model naturally incorporates coupling of electromagnetic radiation to the tunnel currents and, therefore, is particularly suitable for description of the self-coupling effect in Josephson junction. In our numerical calculations we treat the arising integro-differential equation, which describes temporal evolution of the superconducting phase difference coupled to the electromagnetic field, by the Odintsov-Semenov-Zorin algorithm. This allows us to avoid evaluation of the time integrals at each time step while taking into account all the memory effects. To validate the obtained microscopic model of large Josephson junction we focus our attention on the Josephson flux-flow oscillator. The proposed microscopic model of flux-flow oscillator does not involve the phenomenological damping parameter, rather the damping is taken into account naturally in the tunnel current amplitudes calculated at a given temperature. The theoretically calculated current-voltage characteristics is compared to our experimental results obtained for a set of fabricated flux-flow oscillators of different lengths.

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Influence of the passive region on zero field steps for window Josephson junctions

Cited by 14 publications

References 18 publications

Nonlinear waves in networks: Model reduction for the sine-Gordon equation

Nonlinear waves in networks: Model reduction for the sine-Gordon equation

Microscopic Tunneling Model of Nb–AlN–NbN Josephson Flux-Flow Oscillator

Josephson flux-flow oscillator: The microscopic tunneling approach

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