Control of Supercurrent in Hybrid Superconducting–Ferromagnetic Transistors

Nevirkovets, I. P.; Chernyashevskyy, O.; Prokopenko, G.I.; Mukhanov, Oleg A.; Ketterson, J. B.

doi:10.1109/tasc.2015.2390143

Cited by 23 publications

(27 citation statements)

References 38 publications

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“…2. The acceptor CVC is typical for a Josephson tunnel junction, whereas the injector CVC is a straight line, as discussed in our previous works [4] - [8], due to strong suppression of the superconducting correlations in the ferromagnetic layers F 1,2 . Fig.…”

Section: Device Characterizationmentioning

confidence: 59%

“…1 of Ref. [8]. The magnetic moment vs. magnetic field (applied parallel to the layer plane) dependences indicate ferromagnetism in Ni films having a thickness of 2 nm or more and, possibly, superparamagnetism in thinner films [11].…”

Section: Device Characterizationmentioning

confidence: 81%

“…The reason for introducing thin ferromagnetic layers on both sides of the injector junction tunnel barrier is to suppress superconducting correlations across the barrier and thereby achieve simultaneously two goals: (i) to provide good inputoutput isolation, and (ii) to ensure efficient quasiparticle injection into the middle electrode shared by the two junctions (for details see our former publications [4]- [8]). …”

Section: Introductionmentioning

confidence: 99%

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Critical Current Gain in High-jc Superconducting-Ferromagnetic Transistors

Nevirkovets

Shafraniuk

Chernyashevskyy

et al. 2016

IEEE Trans. Appl. Supercond.

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We report experimental and theoretical results on the current gain in superconductor-ferromagnetic transistors (SFTs) with the SISFIFS structure (where S, I, and F denote a superconductor (Nb), an insulator (AlO x ), and a ferromagnetic material (Ni), respectively). The Josephson critical current density, j ca , of the acceptor (SISF) junction in the devices is above 9 kA/cm 2 , which is higher than that in our previous devices. The critical current gain is defined as |δ δ δ δI ca |/|δ δ δ δI i |, where a change |δ δ δ δI i | in the injector (SFIFS junction) current produces a change |δ δ δ δI ca | in the acceptor maximum Josephson current. We observed a smallsignal gain as high as 7.8 and a large-signal current gain of about 2.2. In addition, we found that the Josephson current of the acceptor junction is sensitive to the state of the ferromagnetic layers. A theoretical model is proposed to describe the nonequilibrium processes in the SFT devices, which agrees with the experimental observations. The calculation shows that, in the present device configuration, the dominant contribution to the gap suppression in the middle Nb electrode is due to the quasiparticle injection; spin injection plays a secondary role. We demonstrate that proper device engineering allows one to efficiently control the maximum Josephson current in the SISF acceptor junction using the quasiparticle injection. We conclude that SFT devices can be used as input/output isolators and amplifiers for memory, digital, and RF applications. IndexTerms-Ferromagnetic-superconducting hybrid structures, quasiparticle injection, Josephson effect, proximity effect, superconductivity, superconducting transistor

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Section: Device Characterizationmentioning

confidence: 59%

Section: Device Characterizationmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Critical Current Gain in High-jc Superconducting-Ferromagnetic Transistors

Nevirkovets

Shafraniuk

Chernyashevskyy

et al. 2016

IEEE Trans. Appl. Supercond.

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“…The electric current through the SIS sub-junction of SFT is described by the RCSJ model in terms of the second order differential equations for  . In the SIS, the system oscillates in a potential well, giving rise to sinusoidal current description given by equation (1). The phasedependent Josephson junction energy   U  takes form of the washboard potential, whose slope increases with the bias current I as shown in Fig.…”

Section: Sft Josephson Transistormentioning

confidence: 99%

“…A3 is accomplished using the following parameters. The bit and word line impedances both are 50 Z  , 1 Fig. 7 shows the transient simulation results for the PS/SFT cell depicted in Fig.…”

Section: The Ps/sft Memory Cellmentioning

confidence: 99%

Modeling Computer Memory Based on Ferromagnetic/Superconductor Multilayers

Shafraniuk¹,

Nevirkovets

Mukhanov

2019

Phys. Rev. Applied

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A model of superconducting computer memory exploiting the orthogonal spin transfer (OST) in the pseudospin valve (PS) that is controlled by the three-terminal Josephson superconducting-ferromagnetic transistor (SFT) is developed. The building blocks of the memory are hybrid PS and SFT structures. The memory model is formulated in terms of the equation-defined PS and SFT devices integrated into the PS/SFT memory cell (MC) circuit. Logical units "0" and "1" are associated with the two PS states respectively characterized by two different values of resistance. Elementary logical operations comprising the read/write processes occur when a word pulse applied to the SFT's injector coincides with the respective bit pulse acting on MC. Physically, a word pulse triggers SFT to a resistive state, causing the PS switching between the logical "0" and "1" states. Thus, the whole switching dynamics of MC depends on the non-equilibrium and nonstationary properties of PS and SFT. Modeling the single MC as well as the larger MC-based circuits comprising respectively twelve and thirty elements suggest that such the memory cells can undergo ultrafast switching (sub-ns) and low energy consumption per operation (sub-100 fJ). The suggested model allows studying the influence of noises, punch-through effect, crosstalk, parasitic, etc. The obtained results suggest that the hybrid PS/SFT structures are well-suited to superconducting computing circuits as they are built of magnetic and non-magnetic transition metals and therefore have low impedances (1-30 ). c I achieving much better flexibility of control, as compared to a conventional Josephson junction, where the tilt is controlled only by I . (b) The time dependence of the JJ voltage   V  , where J t   is the dimensionless time, J  is the Josephson plasma frequency. Curves 1, 2, 3, and 4 are related respectively to 0.01, 0.03, 0.033 J   and 0.065. We emphasize that in SFT one can readily alter both, J  and J  by merely changing the injector current. I  for 0.05 J   (curve 1), 0.3 J   (curve 2) and 0.6 J   (curve 3). One can see the hysteresis (curve 4) that is larger for smaller J  . , , J J J J J dimensionless time, J  is the Josephson plasma frequency curves 1, 2, 3, and 4 are related respectively to 0.01, 0.03, 0.033 J   and 0.065. In Fig. 3, we show the time-averaged SFT d.c. return current curves   V  versus   I  for 0.05 J   (curve 1), 0.3 J   (curve 2) and 0.6 J   (curve 3). Remarkably, that in SFT one can readily alter both, J  and J  by merely

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