Josephson effect in superconductor/ferromagnet structures with a complex weak-link region

In this work, we briefly overview various options for Josephson junctions, which should be scalable down to nanometer range for utilization in nanoscale digital superconducting technology. Such junctions should possess high values of critical current, I c , and normal state resistance, R N . Another requirement is the high reproducibility of the junction parameters across a wafer in a fabrication process. We argue that superconductor-normal metal-superconductor (SN -N -NS) Josephson junction of "variable thickness bridge" geometry is a promising choice to meet these requirements. Theoretical analysis of the SN -N -NS junction is performed in the case where the distance between the S electrodes is comparable to the coherence length of the N material. The restriction on the junction geometrical parameters providing the existence of superconductivity in the S electrodes is derived for the current flowing through the junction of an order of I c . The junction heating, as well as available mechanisms for the heat removal, is analyzed. The obtained results show that a SN -N -NS junction with a high (submillivolt) value of I c R N product can be fabricated from a broadly utilized combination of materials like Nb/Cu using well-established technological processes. The junction area can be scaled down to that of semiconductor transistors fabricated in the frame of a 40-nm process.

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“…is the sum [74] of the resistance of the bridge, R NB , and the resistances of two S-N interfaces, R SN ,…”

Section: Calculation Of Sn -N -Ns Junction Supercurrentmentioning

confidence: 99%

Miniaturization of Josephson Junctions for Digital Superconducting Circuits

et al. 2021

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show abstract

“…is the sum [75] of the resistance of the bridge, R nb , and the resistances of two SN interfaces, R sn ,…”

Section: Calculation Of Sn-n-ns Junction Supercurrentmentioning

confidence: 99%

Miniaturization of Josephson junction for digital superconducting circuits

Soloviev¹,

Bakurskiy²,

Ruzhickiy³

et al. 2021

Preprint

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In this work we briefly overview various options for Josephson junctions which should be scalable down to nanometer range for utilization in nanoscale digital superconducting technology. Such junctions should possess high values of critical current, Ic, and normal state resistance, Rn. Another requirement is the high reproducibility of the junction parameters across a wafer in a fabrication process. We argue that Superconductor -Normal metal -Superconductor (SN-N-NS) Josephson junction of "variable thickness bridge" geometry is a promising choice to meet these requirements. Theoretical analysis of SN-N-NS junction is performed in the case where the distance between the S-electrodes is comparable to the coherence length of the N-material. The restriction on the junction geometrical parameters providing the existence of superconductivity in the S-electrodes is derived for the current flowing through the junction of an order of Ic. The junction heating as well as available mechanisms for the heat removal is analyzed. The obtained results show that an SN-N-NS junction with a high (sub-millivolt) value of IcRn product can be fabricated from a broadly utilized combination of materials like Nb/Cu using well-established technological processes. The junction area can be scaled down to that of semiconductor transistors fabricated in the frame of a 40-nm process.

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“…It was suggested recently in [47][48][49][50][51][52] to fabricate 'current in plane' SFS devices having a weak link region consisting of NF or FNF multilayers with the supercurrent flowing parallel to the FN interfaces. In these structures, superconductivity is induced from the S banks into the normal (N) film, while F films serve as a source of spin-polarized electrons, which diffuse from the F-layer to the N-layer, thus providing an effective exchange field in a weak link.…”

Section: Introductionmentioning

confidence: 99%

“…Its strength can be controlled [53,54] by transparencies of NF interfaces, as well as by the products of densities of states at the Fermi level, N F , N N , and film thicknesses, d F , d N . It was shown in [47][48][49][50][51] that the reduction of effective exchange energy in a weak link permits one to increase the decay length from the scale of the order of ∼1 up to ∼100 nm. The calculations performed in these papers did not go beyond a linear approximation in which the amplitude of the second harmonic in the CPR is small.…”

Section: Introductionmentioning

confidence: 99%

Josephson φ-junctions based on structures with complex normal/ferromagnet bilayer

Bakurskiy¹,

Klenov²,

Karminskaya³

et al. 2012

Supercond. Sci. Technol.

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We demonstrate that Josephson devices with nontrivial phase difference 0 < ϕ g < π in the ground state can be realized in structures composed from longitudinally oriented normal metal (N) and ferromagnet (F) films in the weak link region. Oscillatory coupling across F-layer makes the first harmonic in the current-phase relation relatively small, while coupling across N-layer provides negative sign of the second harmonic. To derive quantitative criteria for a ϕ-junction, we have solved two-dimensional boundary-value problem in the frame of Usadel equations for overlap and ramp geometries of S-NF-S structures. Our numerical estimates show that ϕ-junctions can be fabricated using up-to-date technology.

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Josephson effect in superconductor/ferromagnet structures with a complex weak-link region

Cited by 19 publications

References 60 publications

Miniaturization of Josephson Junctions for Digital Superconducting Circuits

Miniaturization of Josephson Junctions for Digital Superconducting Circuits

Miniaturization of Josephson junction for digital superconducting circuits

Josephson φ-junctions based on structures with complex normal/ferromagnet bilayer

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