Proximity-effect engineering in aluminum-based planar Josephson junctions with intrinsic superconductivity

K.B. Polevoy; S.V. Bakurskiy; V.I. Ruzhickiy; S.V. Egorov; A.G. Shishkin; A.S. Frolov; M.A. Kirsanova; I.N. Krupatin; A.V. Yanilkin; N.V. Klenov; I.I. Soloviev; A.A. Golubov; M.Yu. Kupriyanov; V.S. Stolyarov

doi:10.1103/s1k7-wvw2

Proximity-effect engineering in aluminum-based planar Josephson junctions with intrinsic superconductivity

K.B. Polevoy, S.V. Bakurskiy, V.I. Ruzhickiy, S.V. Egorov, A.G. Shishkin, A.S. Frolov, M.A. Kirsanova, I.N. Krupatin, A.V. Yanilkin, N.V. Klenov, I.I. Soloviev, A.A. Golubov, M.Yu. Kupriyanov, V.S. Stolyarov

DOI 10.1103/s1k7-wvw2 · Physical Review Applied

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Abstract

We present a comprehensive study of planar Nb-Al-Nb Josephson junctions with submicrometer dimensions (L≈100 nm, active area of approximately 5×104nm2), where the intrinsic superconductivity of the aluminum weak link plays a crucial role in enhancing device performance. Through a combination of theoretical modeling and experimental characterization, we demonstrate that the aluminum interlayer significantly boosts the critical current Ic≈50μA and the characteristic voltage Vc≈1 mV at T=4 K, while maintaining the nonhysteretic current-voltage characteristics essential for digital applications. Our microscopic model, based on self-consistent solutions of the Usadel equations, reveals that this enhancement originates from the coexistence of proximity-induced superconductivity and intrinsic pairing in aluminum, which is particularly pronounced at an optimal boundary resistance. Structural analysis confirms epitaxial Nb-Al interfaces with minimal interdiffusion, enabling reproducible fabrication of these compact junctions. These results establish Nb-Al-Nb bridges as promising building blocks for high-density superconducting electronics operating at helium temperatures.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.6	Pressure not reported	onset
YBa2Cu3O7-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown