Nonsinusoidal current-phase relations and the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>0</mml:mn><mml:mtext>−</mml:mtext><mml:mi>π</mml:mi></mml:mrow></mml:math>transition in diffusive ferromagnetic Josephson junctions

Mohammadkhani, Ramin; Zareyan, Malek

doi:10.1103/physrevb.73.134503

Cited by 19 publications

(25 citation statements)

References 25 publications

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“…As seen from our results, this may be obtained for the intermediate barrier transparency regime, which agrees with the qualitative conclusions of Ref. 28. However, the effect of uniaxial spin-flip scattering has a detrimental effect on this residual value.…”

Section: Discussionsupporting

confidence: 93%

Role of interface transparency and spin-dependent scattering in diffusive ferromagnet/superconductor heterostructures

2008

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We present a numerical study of the density of states in a ferromagnet/superconductor junction and the Josephson current in a superconductor/ferromagnet/superconductor junction in the diffusive limit by solving the Usadel equation with Nazarov's boundary conditions. Our calculations are valid for an arbitrary interface transparency and arbitrary spin-dependent scattering rate, which allows us to explore the entire proximity-effect regime. We first investigate how the proximity-induced anomalous Green's function affects the density of states in the ferromagnet for three magnitudes of the exchange field h compared to the superconducting gapIn each case, we consider the effect of the barrier transparency and allow for various concentrations of magnetic impurities. We clarify features that may be expected in the various parameter regimes accessible for the ferromagnetic film, with regard to thickness and exchange field. In particular, we address how the zero-energy peak and minigap observed in experiments may be understood in terms of the interplay between the singlet and triplet anomalous Green's function and their dependence on the concentration of magnetic impurities. Our results should serve as a useful tool for quantitative analysis of experimental data. We also investigate the role of the barrier transparency and spin-flip scattering in a superconductor/ferromagnet/superconductor junction. We suggest that such diffusive Josephson junctions with large residual values of the supercurrent at the 0-π transition, where the first harmonic term in the current vanishes, may be used as efficient supercurrentswitching devices. We numerically solve for the Josephson current in such a junction to clarify to what extent this idea may be realized in an experimental setup. It is also found that uniaxial spin-flip scattering has very different effect on the 0-π transition points depending on whether one regards the width-or temperaturedependence of the current. Our theory takes into account vital elements that are necessary to obtain quantitative predictions of the supercurrent in such junctions.

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Section: Discussionsupporting

confidence: 93%

Role of interface transparency and spin-dependent scattering in diffusive ferromagnet/superconductor heterostructures

2008

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“…These two quantities were studied for various geometries by using of quasiclassical Green's function in clean and dirty limits in several works, e.g. 26,27,28,29,30,31,32,33,34,35,36 .…”

Section: Introductionmentioning

confidence: 99%

Spin-polarized Josephson current in superconductor/ferromagnet/superconductor junctions with inhomogeneous magnetization

et al. 2010

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We study numerically the properties of spin-and charge-transport in a current-biased nanoscale diffusive superconductor|ferromagnet|superconductor junction when the magnetization texture is non-uniform. Specifically, we incorporate the presence of a Bloch/Neel domain walls and conical ferromagnetism, including the role of spin-active interfaces. The superconducting leads are assumed to be of the conventional s-wave type. In particular, we investigate how the 0-π transition is influenced by the inhomogeneous magnetization texture and focus on the particular case where the charge-current vanishes while the spin-current is non-zero. In the case of a Bloch/Neel domain-wall, the spin-current can be seen only for one component of the spin polarization, whereas in the case of conical ferromagnetism the spin-current has the three components. This is in contrast to a scenario with a homogeneous exchange field, where the spin-current vanishes completely. We explain all of these results in terms of the interplay between the triplet anomalous Green's function induced in the ferromagnetic region and the local direction of the magnetization vector in the ferromagnet. Interestingly, we find that the spin-current exhibits discontinuous jumps at the 0-π transition points of the critical charge-current. This is seen both in the presence of a domain wall and for conical ferromagnetism. We explain this result in terms of the different symmetry obeyed by the current-phase relation when comparing the charge-and spin-current. Specifically, we find that whereas the charge-current obeys the well-known relation Ic(φ) = −Ic(2π − φ), the spin-current satisfies Is(φ) = Is(2π − φ), where φ is the superconducting phase difference.

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“…The existence of the junction in a superconductor-ferromagnetsuperconductor ͑SFS͒ structure is one of the most interesting phenomena, which occurs for certain thicknesses and exchange fields of the ferromagnet ͑F͒ layer. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] This manifestation is due to the oscillatory behavior of the superconducting pair amplitude and the electronic density of states in the ferromagnet. [4][5][6] In a junction the ground-state phase difference between two coupled superconductors is instead of 0 as in the usual 0-state superconductor-normal-metalsuperconductor ͑SNS͒ junctions.…”

Section: Introductionmentioning

confidence: 99%

“…Later, the nonmonotonic temperature dependence of the critical current in diffusive contacts was observed in other experiments [10][11][12][13][14] and was attributed to the 0-transition induced by the ferromagnetic exchange field. The 0-transition has been studied theoretically by several authors in clean [15][16][17][18] and diffusive [17][18][19][20][21][22][23] Josephson contacts for different conditions and barriers at the FS interfaces.…”

Section: Introductionmentioning

confidence: 99%

Width of the0−πphase transition in diffusive magnetic Josephson junctions

2008

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We investigate the Josephson current between two superconductors ͑S͒ which are connected through a diffusive magnetic junction with a complex structure ͑F c ͒. Using the quantum circuit theory, we obtain the phase diagram of 0 and Josephson couplings for F c being an insulator-ferromagnet-insulator ͑IFI͒ double barrier junction or an IFNFI structure ͑where N indicates a normal-metal layer͒. Compared to a simple SFS structure, we find that the width of the transition, defined by the interval of exchange fields in which a 0transition is possible, is increased by insulating barriers at the interfaces and also by the presence of the additional N layer. The widest transition is found for symmetric F c structures. The symmetric SIFNFIS presents the most favorable condition to detect the temperature-induced 0-transition with a relative width, which is five times larger than that of the corresponding simple SFS structure.

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Nonsinusoidal current-phase relations and the0−πtransition in diffusive ferromagnetic Josephson junctions

Cited by 19 publications

References 25 publications

Role of interface transparency and spin-dependent scattering in diffusive ferromagnet/superconductor heterostructures

Role of interface transparency and spin-dependent scattering in diffusive ferromagnet/superconductor heterostructures

Spin-polarized Josephson current in superconductor/ferromagnet/superconductor junctions with inhomogeneous magnetization

Width of the0−πphase transition in diffusive magnetic Josephson junctions

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