Spin-Dependent Cooper Pair Phase and Pure Spin Supercurrents in Strongly Polarized Ferromagnets

Grein, Roland; Eschrig, Matthias; Metalidis, G.; Schön, Gerd

doi:10.1103/physrevlett.102.227005

Cited by 121 publications

(137 citation statements)

References 32 publications

Supporting

Mentioning

127

Contrasting

Unclassified

Order By: Relevance

“…The spontaneous phase shift of Josephson current has been obtained in several FM/SC systems [25,27,30,35,[41][42][43][44][45][46][47][48][49][50][51][52][53][54]]. Here we demonstrate that this effect is essential only for the case of strong ferromagnets.…”

Section: Spontaneous Josephson Current Through Strong Ferromagnetssupporting

confidence: 53%

See 1 more Smart Citation

Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets

2017

View full text Add to dashboard Cite

Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets Bobkova, I. V.; Silaev, Mikhail Bobkova, I. V., Bobkov, A. M., & Silaev, M. (2017). Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets. Physical Review B, 96 (9) We present the generalized quasiclassical theory of the long-range superconducting proximity effect in heterostructures with strong ferromagnets, where the exchange splitting is of the order of Fermi energy. In the ferromagnet the propagation of equal-spin Cooper pairs residing on the spin-split Fermi surfaces is shown to be governed by the spin-dependent Abelian gauge field which results either from the spin-orbital coupling or from the magnetic texture. This additional gauge field enters into the quasiclassical equations in superposition with the usual electromagnetic vector potential and results in the generation of spontaneous superconducting currents and phase shifts in various geometries which provide the sources of long-range spin-triplet correlations. We derive the Usadel equations and boundary conditions for the strong ferromagnet and consider several generic examples of the Josephson systems supporting spontaneous currents.

show abstract

Section: Spontaneous Josephson Current Through Strong Ferromagnetssupporting

confidence: 53%

“…By now the quasiclassical theory for this regime has been formulated for the case of homogeneous magnetization of the strong ferromagnet [30]. To describe the general situation we go beyond those limitations and consider SC/FM structures with arbitrarily large and spatially inhomogeneous exchange fields.…”

Section: Introductionmentioning

confidence: 99%

Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets

2017

View full text Add to dashboard Cite

show abstract

“…(7), looks similar to the second term in the corresponding equation [Eq. (8)] in the paper by Grein et al [64], where the propagation of the LRTC in a strong ferromagnet with a large Zeeman splitting of energy levels has been considered (see also Ref. 65).…”

mentioning

confidence: 99%

Nematic versus ferromagnetic spin filtering of triplet Cooper pairs in superconducting spintronics

2015

View full text Add to dashboard Cite

We consider two types of magnetic Josephson junctions (JJ). They are formed by two singlet superconductors S and magnetic layers between them so that the JJ is a heterostructure of the S m /n/S m type, where S m includes two magnetic layers with non-collinear magnetization vectors. One layer is represented by a weak ferromagnet and another one-the spin filter-is either conducting strong ferromagnet (nematic or N-type JJ) or magnetic tunnel barrier with spin-dependent transparency (magnetic or M-type JJ). Due to spin filtering only fully polarized triplet component penetrates the normal n wire and provides the Josephson coupling between the superconductors S. Although both filters let to pass triplet Cooper pairs with total spin S parallel to the filter axes, the behavior of nematic and magnetic JJs is completely different. Whereas in the nematic case the charge and spin currents, I Q and I sp , do not depend on mutual orientation of the filter axes, both currents vanish in magnetic JJ in case of antiparallel filter axes, and change sign under reversing the filter direction. The obtained expressions for I Q and I sp show clearly a duality between the superconducting phase ϕ and the angle α between the exchange fields in the weak magnetic layers. PACS numbers: 74.78.Fk, 85.25.Cp, 74.45.+c Triplet Cooper pairing is known to exist in superfluid 3 He [1, 2]. As concerns superconductors, the situation is less clear. Although some indication for the triplet superconductors has been found in a number of completely different classes of materials [3][4][5], a general consensus about the existence of the triplet superconductivity in the organic metals, heavy fermions and other interesting materials investigated from this point of view has not been achieved [6,7]. In principle, the fact that the spins of the fermions of the Cooper pairs are equal to each other does not contradict the Pauli principle because the condensate wave function f (p) and the order parameter ∆ tr (p) in these triplet superconductors are odd functions of the momentum p. In contrast to the conventional BCS superconductivity, the triplet superconductivity with such a symmetry of the order parameter is sensitive to impurity scattering [8] and, therefore, it is usually strongly suppressed by disorder.However, the triplet Cooper pairs can appear already in conventional singlet superconductors provided an external magnetic (H) or an internal exchange (h) field acts on the spins of electrons. [8][9][10][11] A triplet component inevitably arises also in magnetic superconductors [12].The triplet condensate function arising from the singlet superconductivity in the presence of the magnetic or exchange field acting on spins is odd in frequency and therefore may still have an s-wave space symmetry without violating the Pauli principle. It has a component with the 0-spin projection f tr,0 ∝ 〈ĉ ↑ĉ↓ (t ) +ĉ ↓ĉ↑ (t )〉 on the direction of the field h or H but also the components with spin projection ±1. The zero projection component f tr,0 of the condensate functio...

show abstract

“…[11][12][13][14][15] The systems under investigation varied largely in terms of materials and fabrication, the common idea being that a breaking of spin-rotation symmetry around the bulk magnetization axis must somehow be enforced at the superconductor (SC)-ferromagnet (FM) contacts -which is in line with the general theoretical concepts behind this effect 1,[17][18][19][20][21] . In this article, we elaborate on our earlier work concerning long-range triplet supercurrents 22 , where we used a recent extension of the quasiclassical Green function technique 23 , that allows us to consider ferromagnets whose exchange splitting J is of the same order of magnitude as the Fermi energy E F consistently within quasiclassical theory 22,24 . In the following we include additional relevant effects like the suppression of the superconducting energy gap in proximity to the interfaces, the induced magnetization in the superconductor close to the ferromagnet, and disorder in the FM bulk.…”

Section: Introductionmentioning

confidence: 99%

Inverse proximity effect and influence of disorder on triplet supercurrents in strongly spin-polarized ferromagnets

2013

View full text Add to dashboard Cite

We discuss the Josephson effect in strongly spin-polarized ferromagnets where triplet correlations are induced by means of spin-active interface scattering, extending our earlier work [R. Grein et al., Phys. Rev. Lett. 102, 227005 (2009)] by including impurity scattering in the ferromagnetic bulk and the inverse proximity effect in a fully self-consistent way. Our quasiclassical approach accounts for the differences of Fermi momenta and Fermi velocities between the two spin bands of the ferromagnet, and thereby overcomes an important short-coming of previous work within the framework of Usadel theory. We show that non-magnetic disorder in conjunction with spindependent Fermi velocities may induce a reversal of the spin-current as a function of temperature.

show abstract

Spin-Dependent Cooper Pair Phase and Pure Spin Supercurrents in Strongly Polarized Ferromagnets

Cited by 121 publications

References 32 publications

Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets

Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets

Nematic versus ferromagnetic spin filtering of triplet Cooper pairs in superconducting spintronics

Inverse proximity effect and influence of disorder on triplet supercurrents in strongly spin-polarized ferromagnets

Contact Info

Product

Resources

About