Nonequilibrium transport in superconductor/ferromagnet/superconductor diffusive junctions: Interplay between proximity effect and ferromagnetism

Bobkova, I. V.; Bobkov, A. M.

doi:10.1103/physrevb.74.220504

Cited by 7 publications

(4 citation statements)

References 29 publications

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“…85 To some extent, from the mathematical point of view, the voltage V is analogous to the exchange field h. The form of the I -V curve for an S/F/S Josephson contact has been found in Ref. 86.…”

Section: A Josephson Current In S M /Fl/n/fl/s M Junctionsmentioning

confidence: 99%

Josephson effect in multiterminal superconductor-ferromagnet junctions coupled via triplet components

2016

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On the basis of the Usadel equation we study a multi-terminal Josephson junction. This junction is composed by "magnetic" superconductors S m which have singlet pairing and are separated from the normal n wire by spin filters so that the Josephson coupling is caused only by fully polarized triplet components. We show that there is no interaction between triplet Cooper pairs with antiparallel total spin orientations. The presence of an additional singlet superconductor S attached to the n wire leads to a finite Josephson current I Q with an unusual current-phase relation. The density of states in the n wire for different orientations of spins of Cooper pairs is calculated. We derive a general formula for the current I Q in a multi-terminal Josephson contact and apply this formula for analysis of two four-terminal Josephson junctions of different structures. It is shown in particular that both the "nematic" and the "magnetic" cases can be realized in these junctions. In a two-terminal structure with parallel filter orientations and in a three-terminal structure with antiparallel filter orientations of the "magnetic" superconductors with attached additional singlet superconductor, we find a nonmonotonic temperature dependence of the critical current. Also, in these structures, the critical current shows a Riedel peak like dependence on the exchange field in the "magnetic" superconductors. Although there is no current through the S/n interface due to orthogonality of the singlet and triplet components, the phase of the order parameter in the superconuctor S is shown to affect the Josephson current in a multi-terminal structure.

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Section: A Josephson Current In S M /Fl/n/fl/s M Junctionsmentioning

confidence: 99%

Josephson effect in multiterminal superconductor-ferromagnet junctions coupled via triplet components

2016

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“…In the anti-ferromagnetic alignment of the magnetizations of the F layers a strong suppression of superconductivity was found, leading to a large magnetoresistive effect. In Josephson junctions the effect of spin injection 27 and presence of weak ferromagnets 28 was considered, while the effect of Andreev reflection on spin accumulation in a ferromagnetic wire was reported in Ref. 29.…”

Section: Introductionmentioning

confidence: 99%

Nonequilibrium spin-dependent phenomena in mesoscopic superconductor–normal metal tunnel structures

et al. 2007

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We analyze the broad range of spin-dependent nonequilibrium transport properties of hybrid systems composed of a normal region tunnel coupled to two superconductors with exchange fields induced by the proximity to thin ferromagnetic layers and highlight its functionalities. By calculating the quasiparticle distribution functions in the normal region we find that they are spin-dependent and strongly sensitive to the relative angle between exchange fields in the two superconductors. The impact of inelastic collisions on their properties is addressed. As a result, the electric current flowing through the system is found to be strongly dependent on the relative angle between exchange fields, giving rise to a huge value of magnetoresistance. Moreover, the current presents a complete spin-polarization in a wide range of bias voltages, even in the quasiequilibrium case. In the nonequilibrium limit we parametrize the distributions with an "effective" temperature, which turns out to be strongly spin-dependent, though quite sensitive to inelastic collisions. By tunnel coupling the normal region to an additional superconducting electrode we show that it is possible to implement a spin-polarized current source of both spin species, depending on the bias voltages applied. 74.50.+r,05.70.Ln

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“…The degree of ac current spin polarization, calculated according to Eq. (17), is represented in inserts to Figs. 3(a) and 3(b) at x = d/2 and x = 0, respectively.…”

mentioning

confidence: 99%

“…In particular, it was shown that by tunnel coupling of the normal regions of two superconductor-normal metal-ferromagnet trilayers the absolute spin-valve effect can be realized for a certain interval of voltages applied between the normal regions 16 . For voltage-biased superconductor-weak ferromagnet-superconductor Josephson junction the interplay between the proximity effect and the Zeeman exchange field results in additional peak-like features in the I-V characteristics 17 . The ac Josephson current in superconductor-ferromagnet-superconductor voltage biased junction was also studied 18 .…”

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confidence: 99%

Proximity-driven source of highly spin-polarized ac current on the basis of superconductor/weak ferromagnet/superconductor voltage-biased Josephson junction

Bobkov

Bobkova

2008

Jetp Lett.

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We theoretically investigate an opportunity to implement a source of highly spin-polarized ac current on the basis of superconductor/weak ferromagnet/superconductor (SFS) voltage-biased junction in the regime of essential proximity effect and calculate the current flowing through the probe electrode tunnel coupled to the ferromagnetic interlayer region. It is shown that while the polarization of the dc current component is generally small in case of weak exchange field of the ferromagnet, there is an ac component of the current in the system. This ac current is highly spin-polarized and entirely originated from the non-equilibrium proximity effect in the interlayer. The frequency of the current is controlled by the voltage applied to SFS junction. We discuss a possibility to obtain a source of coherent ac currents with a certain phase shift between them by tunnel coupling two probe electrodes at different locations of the interlayer region. PACS numbers: 74.50.+r, 74.45.+c Various proximity and transport phenomena in hybrid structures containing superconducting and ferromagnetic elements are currently in the spotlight. The equilibrium transport and proximity effect in such structures have been theoretically and experimentally investigated recently in details as for the case of weak ferromagnetic alloys (see Ref. 1 and references therein) so as for halfmetals like CrO 2 2,3 .Spin-dependent properties of nonequilibrium systems are also actively investigated. In particular, the spin imbalance induced in a ferromagnet (F) in nonequilibrium conditions was studied in ferromagnet-superconductorferromagnet (FSF) junctions 4,5,6,7,8,9 . It was found that antiferromagnetic alignment of the exchange fields of the ferromagnets strongly suppresses superconductivity, which leads to large magnetoresistive effect. The influence of the interplay between Andreev reflection at the interface and spin accumulation close to the interface was investigated 10 . The effect of spin injection in Josephson junctions was considered 11 . The papers 9,12 have theoretically studied the spin relaxation due to spin-flip scattering.The authors of 13,14 propose the possibility of manipulating magnetization of a mesoscopic normal (N) region through the Zeeman splitting of superconducting density of states and applied voltage in voltage biased SNS or FSNSF tunnel junctions. Also, the spin-polarized transport through superconductor-normal metal hybrid structures, where the density of states in a superconductor is Zeeman-splitted, was investigated 13,14,15 . It was shown that, in alternative to half-metallic ferromagnets, such junction can be used to generate highly spin-polarized currents, which are tunable in magnitude and sign by the bias voltage and exchange field. In 13,14 the normal metal region between the superconducting leads has been considered to be long enough in order to suppress the proximity effect and, consequently, ac Josephson effect in it. However, if the junction length is of the order of superconducting coherence length ξ = D/∆,...

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Nonequilibrium transport in superconductor/ferromagnet/superconductor diffusive junctions: Interplay between proximity effect and ferromagnetism

Cited by 7 publications

References 29 publications

Josephson effect in multiterminal superconductor-ferromagnet junctions coupled via triplet components

Josephson effect in multiterminal superconductor-ferromagnet junctions coupled via triplet components

Nonequilibrium spin-dependent phenomena in mesoscopic superconductor–normal metal tunnel structures

Proximity-driven source of highly spin-polarized ac current on the basis of superconductor/weak ferromagnet/superconductor voltage-biased Josephson junction

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