Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Applied Physics

Investigation of dc Josephson current distribution in double-barrier three-terminal devices with a thin middle superconducting layer

Ivan P. Nevirkovets, T. Doderer, A. Laub, Mark G. Blamire, Jan E. Evetts

Published Aug 15, 1996• 5 citations
Publisher

Abstract

Nb/Al–AlOx–Nb/Al–AlOx–Nb double-barrier three-terminal Josephson devices with a thin middle Nb/Al bilayer, which have potential for use as switching and amplifying elements in superconducting electronics, have been investigated in the stationary state by means of low-temperature scanning electron microscopy. For the devices with lateral sizes comparable with the effective Josephson penetration depth, we observed nearly homogeneous current distribution over the region common to the top and bottom junctions when the devices were biased across both the barriers in the absence of an external magnetic field. When the two junctions are biased separately, the current is concentrated at the junction edges in accordance with the behavior characteristic of distributed junctions. In an applied magnetic field, the vortex structure is confined to the area shared by both junctions when the device is biased as a whole. The experiment gives an indication that in the stationary state the spatial phase difference distribution of the two junctions coincides in the shared region at least in some interval of the external magnetic field.

DOI
10.1063/1.363064

Related papers

Double barrier long Josephson junctions with a contact to the intermediate superconducting layer

H. Kohlstedt, Alexey Vladimirovich Ustinov, F. Peter

We demonstrate a double barrier long Josephson tunnel junction device of overlap geometry with an external electric contact to the middle electrode. The junctions were fabricated with a standard Nb/Al-AlO/sub x//Nb process. To exhibit fluxon coupling effects in stacked junctions, the intermediate Nb layer thickness between two barriers has to be of the order of the London penetration depth, i.e. 90 nm for sputtered Nb films. By using a planarization process, we were able to avoid steep steps on the wafer and so to reduce the intermediate layer thickness to 90 nm. Double-junction stacks with areas from 10/spl times/10 /spl mu/m/sup 2/ to 20/spl times/600 /spl mu/m/sup 2/ were fabricated. In the best stacks, the difference in the critical currents of two junctions was less than 3%. Clear voltage locking effects were observed in current-voltage (I-V) characteristics.>

IEEE Transactions on Applied Superconductivity•Jun 1, 1995•5 citations

Multi-Terminal Superconducting Nonequilibrium Device With a Ferromagnetic Screen

Ivan P. Nevirkovets, O. Chernyashevskyy, John B. Ketterson +1 more

We have fabricated and characterized double-barrier multi-terminal superconducting transistor-like devices with the Nb/Al/AlOx/Al/Nb/Ni/Al/AlOx/Al/Nb (S1IS2FIS3) structure, where S, I, and F refer to superconducting, insulating, and ferromagnetic layers, respectively. A thin ferromagnetic Ni layer screens the superconductivity of the middle Nb layer on the injector-barrier side, so that the Nb/Ni bilayer manifests itself as a superconductor in the current-voltage characteristic (I-V curve) of the acceptor S1IS2junction, but as a normal metal in the I-V curve of the injector S2FIS3junction. It is shown that this property allows for considerable improvement of the input-output isolation of the quasiparticle-injection devices as compared with that for the formerly reported quiteron.

IEEE Transactions on Applied Superconductivity•Nov 17, 2010•1 citation

Three-terminal Josephson device with direct bias-current controlled phase difference

Ivan P. Nevirkovets, Mark G. Blamire, Jan E. Evetts

We have fabricated and characterized the Nb/Al-AlO/sub x/-Nb/Al-AlO/sub x/-Nb three-terminal double junction Josephson device in which the phase difference across the whole device is controlled by the tunnel current flowing through one of the junctions. The device reveals current gain about 10 and has good isolation of the input and output circuits.>

IEEE Transactions on Applied Superconductivity•Jun 1, 1995•6 citations

Stacked Josephson junctions in view of macroscopic quantum experiments

C. Granata, Valentina Corato, A. Monaco +3 more

We present Nb/AlOx/Nb–Al/AlOx/Nb stacked Josephson junctions which we propose as three-terminal elements to control the quantum behavior of Josephson complex systems. A bias current can be independently injected in the “top” junction, providing a fine control of the critical current of the “bottom” junction. The reported characterization of the device refers to data in the classical limit including measurements of the switching dynamics between metastable states of the system at different temperatures and bias conditions. At low temperature, the effective dissipation of the bottom junction remains substantially unchanged when different injection currents flow in the top junction. These results are interesting to project new configurations of macroscopic quantum experiments.

Applied Physics Letters•Aug 20, 2001•22 citations

Characterization of Superconducting Josephson Junctions on Electro-Optic LiNbO 3 Substrates at mK Temperatures

Saba Kousar, Roberta Satariano, G. Ausanio +5 more

We report on the fabrication and millikelvin char acterization of Nb/Al–AlOx/Nb Josephson junctions directly de posited on X-cut LiNbO3 substrates. Motivated by the strong electro-optic and piezoelectric properties of LiNbO3, such devices are of interest for future hybrid superconducting–electro-optic architectures. The junctions were fabricated using standard processes involving DC magnetron sputtering followed by controlled thermal oxidation of the aluminum layer to form an AlOx tunnel barrier with reproducible junction areas. Insulation of the junctions was achieved by anodization and SiOx deposition. Electrical measurements performed at 30 mK reveal high-quality Josephson tunnel junction behavior with a critical current density ofJc= 70 A/cm2and a characteristic voltage reaching values up toVm= 286 mV. Differential conductance measurements exhibit pronounced quasiparticle peaks corresponding to a sum gap energy of 2Δ = (2.73 ± 0.05) meV, confirming the good quality of the Nb electrodes. Magnetic-field-dependent measure ments yield a Josephson penetration depth of λJ= 45 μm, confirming operation in the small-junction regime, with deviations from the ideal Josephson interference pattern attributed to non-uniform current distribution across the junction area. Compared to our previous characterization at 4.2 K, this work demonstrates reliable Josephson junction operation on LiNbO3 at dilution-refrigerator temperatures relevant for quantum circuits, supporting the suitability of lithium niobate as a promising substrate for future hybrid superconducting–electro-optic device implementations.

IEEE Transactions on Applied Superconductivity•Feb 23, 2026•0 citations

Improved Characteristics of Intrinsically Shunted ${\rm Nb/Al}-{\rm AlO}_{x}-{\rm Nb}$ Josephson Junctions

V. Lacquaniti, Natascia De Leo, Matteo Fretto +3 more

Josephson junctions with non-hysteretic current-voltage characteristics form the basis of most superconducting electronic circuits including RSFQ logic and programmable Josephson voltage standards. In contrast to conventional SIS devices, Nb/Al-AlOx-Nb (SNIS) junctions with an additional comparatively thick Al interlayer and a comparatively thin barrier AlOxare intrinsically shunted at T ≥ 4.2 K . In this contribution, we provide experimental and theoretical arguments proving that this finding is mainly explained by a broad distribution of highly-conductive barrier transparencies with a significant effect from nearly ballistic modes. An additional advantage of the proposed SNIS junctions is possibility to tune the critical voltage value by modifying Nb and/or Al film thicknesses. With observations of wide Shapiro steps up to 1.25 V at 6.3 K we show that this type of Josephson junctions can be successfully used at temperatures above 4.2 K. The presence of well-developed quantized voltage features even at 7.2 K means that Nb/Al-AlOx-Nb devices can successfully operate far above the liquid helium temperature and, in principle, are compatible with two-stage cryocoolers.

IEEE Transactions on Applied Superconductivity•Nov 9, 2010•2 citations
Nb/Al–AlOx–Nb/Al–AlOx–Nb double-barrier three-terminal Josephson devices with a thin middle Nb/Al bilayer, which have potential for use as switching and amplifying elements in superconducting electronics, have been investigated in the stationary state by means of low-temperature scanning electron microscopy. For the devices with lateral sizes comparable with the effective Josephson penetration depth, we observed nearly homogeneous current distribution over the region common to the top and bottom junctions when the devices were biased across both the barriers in the absence of an external magnetic field. When the two junctions are biased separately, the current is concentrated at the junction edges in accordance with the behavior characteristic of distributed junctions. In an applied magnetic field, the vortex structure is confined to the area shared by both junctions when the device is biased as a whole. The experiment gives an indication that in the stationary state the spatial phase difference distribution of the two junctions coincides in the shared region at least in some interval of the external magnetic field.
We demonstrate a double barrier long Josephson tunnel junction device of overlap geometry with an external electric contact to the middle electrode. The junctions were fabricated with a standard Nb/Al-AlO/sub x//Nb process. To exhibit fluxon coupling effects in stacked junctions, the intermediate Nb layer thickness between two barriers has to be of the order of the London penetration depth, i.e. 90 nm for sputtered Nb films. By using a planarization process, we were able to avoid steep steps on the wafer and so to reduce the intermediate layer thickness to 90 nm. Double-junction stacks with areas from 10/spl times/10 /spl mu/m/sup 2/ to 20/spl times/600 /spl mu/m/sup 2/ were fabricated. In the best stacks, the difference in the critical currents of two junctions was less than 3%. Clear voltage locking effects were observed in current-voltage (I-V) characteristics.>
We have fabricated and characterized double-barrier multi-terminal superconducting transistor-like devices with the Nb/Al/AlOx/Al/Nb/Ni/Al/AlOx/Al/Nb (S1IS2FIS3) structure, where S, I, and F refer to superconducting, insulating, and ferromagnetic layers, respectively. A thin ferromagnetic Ni layer screens the superconductivity of the middle Nb layer on the injector-barrier side, so that the Nb/Ni bilayer manifests itself as a superconductor in the current-voltage characteristic (I-V curve) of the acceptor S1IS2junction, but as a normal metal in the I-V curve of the injector S2FIS3junction. It is shown that this property allows for considerable improvement of the input-output isolation of the quasiparticle-injection devices as compared with that for the formerly reported quiteron.
We present Nb/AlOx/Nb–Al/AlOx/Nb stacked Josephson junctions which we propose as three-terminal elements to control the quantum behavior of Josephson complex systems. A bias current can be independently injected in the “top” junction, providing a fine control of the critical current of the “bottom” junction. The reported characterization of the device refers to data in the classical limit including measurements of the switching dynamics between metastable states of the system at different temperatures and bias conditions. At low temperature, the effective dissipation of the bottom junction remains substantially unchanged when different injection currents flow in the top junction. These results are interesting to project new configurations of macroscopic quantum experiments.
We report on the fabrication and millikelvin char acterization of Nb/Al–AlOx/Nb Josephson junctions directly de posited on X-cut LiNbO3 substrates. Motivated by the strong electro-optic and piezoelectric properties of LiNbO3, such devices are of interest for future hybrid superconducting–electro-optic architectures. The junctions were fabricated using standard processes involving DC magnetron sputtering followed by controlled thermal oxidation of the aluminum layer to form an AlOx tunnel barrier with reproducible junction areas. Insulation of the junctions was achieved by anodization and SiOx deposition. Electrical measurements performed at 30 mK reveal high-quality Josephson tunnel junction behavior with a critical current density ofJc= 70 A/cm2and a characteristic voltage reaching values up toVm= 286 mV. Differential conductance measurements exhibit pronounced quasiparticle peaks corresponding to a sum gap energy of 2Δ = (2.73 ± 0.05) meV, confirming the good quality of the Nb electrodes. Magnetic-field-dependent measure ments yield a Josephson penetration depth of λJ= 45 μm, confirming operation in the small-junction regime, with deviations from the ideal Josephson interference pattern attributed to non-uniform current distribution across the junction area. Compared to our previous characterization at 4.2 K, this work demonstrates reliable Josephson junction operation on LiNbO3 at dilution-refrigerator temperatures relevant for quantum circuits, supporting the suitability of lithium niobate as a promising substrate for future hybrid superconducting–electro-optic device implementations.
Improved Characteristics of Intrinsically Shunted Nb/Al−AlOx−Nb{\rm Nb/Al}-{\rm AlO}_{x}-{\rm Nb}Nb/Al−AlOx​−Nb Josephson Junctions
Josephson junctions with non-hysteretic current-voltage characteristics form the basis of most superconducting electronic circuits including RSFQ logic and programmable Josephson voltage standards. In contrast to conventional SIS devices, Nb/Al-AlOx-Nb (SNIS) junctions with an additional comparatively thick Al interlayer and a comparatively thin barrier AlOxare intrinsically shunted at T ≥ 4.2 K . In this contribution, we provide experimental and theoretical arguments proving that this finding is mainly explained by a broad distribution of highly-conductive barrier transparencies with a significant effect from nearly ballistic modes. An additional advantage of the proposed SNIS junctions is possibility to tune the critical voltage value by modifying Nb and/or Al film thicknesses. With observations of wide Shapiro steps up to 1.25 V at 6.3 K we show that this type of Josephson junctions can be successfully used at temperatures above 4.2 K. The presence of well-developed quantized voltage features even at 7.2 K means that Nb/Al-AlOx-Nb devices can successfully operate far above the liquid helium temperature and, in principle, are compatible with two-stage cryocoolers.