Josephson currents through spin-active interfaces

Fogelström, Mikael

doi:10.1103/physrevb.62.11812

Cited by 148 publications

(229 citation statements)

References 31 publications

Supporting

Mentioning

219

Contrasting

Order By: Relevance

“…25 the transport properties of a S/F junction were calculated by using the Blonder-Tinkham-Klapwijk formalism. 26 This analysis was extended in several other works [27][28][29][30][31][32][33] for S/F and S/F /S junctions in the ballistic and diffusive limit by taking into account spin-active interfaces between the F and S layers. 34,35 In particular, the results for the diffusive limit presented in those works have been obtained by using the boundary conditions for the quasiclassical Green's functions derived in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Surprisingly, in spite of many works on N/S and F /S structures such boundary conditions are absent in the literature. [27][28][29][30][31]34,35,54,55 In order to fill this gap, we present here a heuristic derivation of the boundary conditions at the S M /I sf /S M interface, which can also be used for N/I sf /S or S-I sf -F /S interfaces.…”

Section: Subgap Conductance In N/i Sf /S Junctions: Effective Boumentioning

confidence: 99%

See 1 more Smart Citation

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

2012

View full text Add to dashboard Cite

We present a theoretical study of the quasiparticle and subgap conductance of generic X/I sf /S M junctions with a spin-filter barrier I sf , where X is either a normal N or a ferromagnetic metal F and S M is a superconductor with a built-in exchange field. Our study is based on the tunneling Hamiltonian and the Green's-function technique. First, we focus on the quasiparticle transport, both above and below the superconducting critical temperature. We obtain a general expression for the tunneling conductance which is valid for arbitrary values of the exchange field and arbitrary magnetization directions in the electrodes and in the spin-filter barrier. In the second part, we consider the subgap conductance of a N/I sf /S junction, where S is a conventional superconductor. In order to account for the spin-filter effect at interfaces, we heuristically derive boundary conditions for the quasiclassical Green's functions. With the help of these boundary conditions, we show that the proximity effect and the subgap conductance are suppressed by spin filtering in a N/I sf /S junction. Our work provides useful tools for the study of spin-polarized transport in hybrid structures both in the normal and in the superconducting state.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Subgap Conductance In N/i Sf /S Junctions: Effective Boumentioning

confidence: 99%

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

2012

View full text Add to dashboard Cite

show abstract

“…22 However, the conditions in Ref. 21 were only derived for the equilibrium (retarded and advanced) propagators. Furthermore, even in equilibrium situations they can not be used in the published form in the case when the two sides of the interface have a different number of trajectories (i.e.…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…Progress towards a more convenient form of boundary conditions has been made by Eschrig (nonmagnetic interfaces) 20 and Fogelström (magnetic interfaces). 21 They employed the powerful Riccati parameterization method which allows for a considerably simpler representation of boundary conditions in terms of the Riccati amplitudes. 22 However, the conditions in Ref.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Transfer-matrix description of heterostructures involving superconductors and ferromagnets

et al. 2004

View full text Add to dashboard Cite

Based on the technique of quasiclassical Green's functions, we construct a theoretical framework for describing heterostructures consisting of superconductors and/or spin-polarized materials. The necessary boundary conditions at the interfaces separating different metals are formulated in terms of hopping amplitudes in a t-matrix approximation. The theory is applicable for an interface with arbitrary transmission and exhibiting scattering with arbitrary spin dependence. Also, it can be used in describing both ballistic and diffusive systems. We establish the connection between the standard scattering-matrix approach and the existing boundary conditions, and demonstrate the advantages offered by the t-matrix description.

show abstract

“…Magnetic interfaces can not be characterized by the only parameter D and Andreev bound states are known to take place on the magnetic surface of s-wave superconductor 20 . So it is natural that new qualitative features with respect to nonmagnetic case appear in dc current even in the simplest models of a short magnetic junction 21,22 .…”

mentioning

confidence: 99%

Subharmonic gap structure in superconductor/ferromagnet/superconductor junctions

Bobkova

2006

Phys. Rev. B

View full text Add to dashboard Cite

The behavior of dc subgap current in magnetic quantum point contact is discussed for the case of low-transparency junction with different tunnel probabilities for spin-up (D ↑ ) and spin-down (D ↓ ) electrons. Due to the presence of Andreev bound states ±ε0 in the system the positions of subgap electric current steps eVn = (∆ ± ε0)/n are split at temperature T = 0 with respect to the nonmagnetic result eVn = 2∆/n. It is found that under the condition D ↑ = D ↓ the spin current also manifests subgap structure, but only for odd values of n. The split steps corresponding to n = 1, 2 in subgap electric and spin currents are analytically calculated and the following steps are described qualitatively.PACS numbers: 74.45.+c, 74.50.+r It is well established now that subharmonic gap structure in superconducting weak links can be described in terms of multiple Andreev reflection (MAR). The concept of MAR was first introduced 1 for SNS (superconductor -normal metal -superconductor) junctions and then extended to include the effect of resistance of SN interface 2 (OTBK theory). Then it was shown 3 that this mechanism is the reason for subharmonic gap structures in junctions of any type, and specifically in superconducting point contacts. As long as the junction is short on the scale of the coherence length ξ 0 the microscopic details of the junction are irrelevant and for the nonmagnetic junction the only parameter is the transmission probability of the barrier D. An exact theory of MAR for short nonmagnetic junctions between clean superconductors has been developed in Refs.4,5 on the basis of scattering amplitudes method and in Ref.6 making use of nonequilibrium Green function techniques. It was obtained that for this case MAR manifests itself in dc current as current steps at voltages eV n = 2∆/n, n = 1, 2, .... The magnitude of the current onset at V n is proportional to D n . The theoretical results are consistent with the experimental situation in atomic-size superconducting point contacts 7,8,9,10 . The subharmonic gap structure due to photon-assisted MAR in the presence of microwave radiation has also been studied and theoretical predictions 11 are confirmed by the experimental observations 12 .Arnold 3 was the first to take into account the phase coherence of subsequent Andreev reflections, which were absent in the OTBK theory. The quantum coherence in short ballistic junctions lead to ac Josephson effect 4,5,6 . In addition, in long ballistic SNS junctions coherence effects give rise to resonant structures in the dc current due to Andreev quantization 13 .MAR in diffusive nonmagnetic junctions has also been investigated in details. Short diffusive junctions with Thouless energy E T h ≫ ∆ can be described by coherent MAR theory and show subharmonic gap structures at eV n = 2∆/n 14,15 . In long diffusive junctions with E T h ∆ additional peaks in the differential conductance at eV n ≈ 2(∆ ± E T h )/2n are predicted 16 . This result is in qualitative agreement with the experimental data 17 . The incoherent MAR regi...

show abstract

Josephson currents through spin-active interfaces

Cited by 148 publications

References 31 publications

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

Transfer-matrix description of heterostructures involving superconductors and ferromagnets

Subharmonic gap structure in superconductor/ferromagnet/superconductor junctions

Contact Info

Product

Resources

About