Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization

Иванов, Д. А.; Fominov, Ya. V.

doi:10.1103/physrevb.73.214524

Cited by 81 publications

(142 citation statements)

References 12 publications

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“…Moreover, previous works have considered analytical solutions of the Usadel equation using the so-called θ -parametrization in SN bilayers161718 and also approximate solutions in the SNS case192021, whereas in our work the analytical solution is exact for the key cases of (i) and (ii) for phase differences nπ between the terminals.…”

Section: Theorymentioning

confidence: 99%

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n-terminal Josephson junctions

Amundsen

Ouassou

Linder

2017

Sci Rep

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Multiterminal Josephson junctions have recently been proposed as a route to artificially mimic topological matter with the distinct advantage that its properties can be controlled via the superconducting phase difference, giving rise to Weyl points in 4-terminal geometries. A key goal is to accurately determine when the system makes a transition from a gapped to non-gapped state as a function of the phase differences in the system, the latter effectively playing the role of quasiparticle momenta in conventional topological matter. We here determine the proximity gap phase diagram of diffusive n-terminal Josephson junctions ( ∈ N n ), both numerically and analytically, by identifying a class of solutions to the Usadel equation at zero energy in the full proximity effect regime. We present an analytical equation which provides the phase diagram for an arbitrary number of terminals n. After briefly demonstrating the validity of the analytical approach in the previously studied 2-and 3-terminal cases, we focus on the 4-terminal case and map out the regimes where the electronic excitations in the system are gapped and non-gapped, respectively, demonstrating also in this case full agreement between the analytical and numerical approach.The interest in topological quantum phases of matter has grown steadily in recent years, and the fundamental importance of this topic in physics was recently recognized by Thouless, Haldane, and Kosterlitz being awarded the 2016 Nobel prize in physics for their contribution to this field. So far, specific material classes such as telluride-based quantum wells (HgTe, CdTe), bismuth antimony (Bi 1−x Sb x ) and bismuth selenide (Bi 2 Se 3 ) have received the most attention in the pursuit of symmetry-protected topological phases and excitations 1-4 . However, it was recently proposed 5 that similar physics could be obtained using conventional superconducting materials. More specifically, by using multiterminal Josephson junctions, the authors of ref. 5 showed that it was possible to create an artificial topological material displaying Weyl singularities under appropriate conditions. In multiterminal Josephson junctions hosting well-defined Andreev bound states, the crossing of these states with the Fermi level has been shown to be analogous to Weyl points in 3D solids with the Andreev bound state taking on the role of energy bands and the superconducting phase differences corresponding to quasiparticle momenta. A considerable advantage in utilizing multiterminal Josephson junctions rather than 3D solids to study exotic phenomena such as Weyl singularities and topologically different phases is that the phase differences are much more easily controlled experimentally than the quasiparticle momenta.In order to probe electronic excitations with topological properties, a key goal is to map out the phase diagram of the system in terms of when it is gapped or not. A gapped system here means that there are no available excitations in a finite interval around the Fermi level. The reason for why this...

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Section: Theorymentioning

confidence: 99%

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n-terminal Josephson junctions

Amundsen

Ouassou

Linder

2017

Sci Rep

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“…However, in case of textured ferromagnets the Green's function becomes non-diagonal in spin space and the parametrization via two angles fails to work. An appropriate generalization of this parametrization was proposed in [49] and takes the form: are the components of the gauge field a, which can be viewed as an effective spin-orbit coupling [50]. Equations…”

Section: Dos In Diffusive Spin-textured S/f Bilayers 21 Model and Mmentioning

confidence: 99%

Signatures of spin-triplet Cooper pairing in the density of states of spin-textured superconductor-ferromagnet bilayers

2019

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The existence of spin-triplet superconductivity in non-collinear magnetic heterostructures with superconductors is by now well established. This observation lays the foundation of superconducting spintronics with the aim to create a low-power consuming devices in order to replace the conventional electronics limited by heating. From a fundamental point of view the investigation of the structure and properties of spin-triplet Cooper pairs continues. Recently, spectroscopic evidence has shown to offer more detailed insights in the structure of triplet Cooper pairs than the supercurrent. Hence, we study here the structure of spin-triplet Cooper pairs through the density of states (DOS) in bilayers of a textured magnetic insulator in proximity to a superconductor. Using quasiclassical Green function methods, we study the local DOS, both spin-resolved and spin-independent. We show that the equalspin and mixed-spin triplet Cooper pairs leads to different spectroscopic signatures, which can be further enhanced by spin-polarized spectroscopy. Our results show the huge potential spin-polarized tunneling methods offer in characterizing unconventional superconductivity in heterostructures.

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“…II C) reveal that components of f parallel to h are affected by the magnetization while the components perpendicular to it remain unaffected. 63 Since we consider magnetic configurations in which the magnetization vector h(x) rotates in the yz plane, we present the Gor'kov vector f (x) either in the fixed Cartesian system or in the rotating basis {x, e ⊥ (x), e (x)} (see Fig. 1), where the ⊥ ( ) index denotes the component perpendicular (parallel) to the local direction of the magnetization h(x) in the yz plane.…”

Section: 2mentioning

confidence: 99%

“…In particular, whenever the magnetization changes direction, long range correlations involving |1, ±1 states are generated. 10,11 To include these correlations, it is convenient to consider the Ivanov-Fominov parametrization of the Green and Gor'kov functions 63,73 …”

Section: Usadel's Equation For Inhomogeneous Magnetizationsmentioning

confidence: 99%

Classification of magnetic inhomogeneities and0−πtransitions in superconducting-magnetic hybrid structures

2016

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We present a comparative study of pair correlations and currents through superconductingmagnetic hybrid systems with a particular emphasis on the tunable Bloch domain wall of an exchange spring. This study of the Gor'kov functions contrasts magnetic systems with domain walls that change at discrete points in the magnetic region with those that change continuously throughout. We present results for misaligned homogeneous magnetic multilayers, including spin valves, for discrete domain walls, as well as exchange springs and helical domain walls -such as Holmiumfor the continuous case. Introducing a rotating basis to disentangle the role of singlet and triplet correlations, we demonstrate that substantial amounts of (so-called short range) singlet correlations are generated throughout the magnetic system in a continuous domain wall via the cascade effect. We propose a classification of 0 − π transitions of the Josephson current into three types, according to the predominant pair correlations symmetries involved in the current. Properties of exchange springs for an experimental study of the proposed effects are discussed. The interplay between components of the Gor'kov function that are parallel and perpendicular to the local magnetization lead to a novel prediction about their role in a proximity system with a progressively twisting helix that is experimentally measurable.

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Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization

Cited by 81 publications

References 12 publications

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n-terminal Josephson junctions

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n-terminal Josephson junctions

Signatures of spin-triplet Cooper pairing in the density of states of spin-textured superconductor-ferromagnet bilayers

Classification of magnetic inhomogeneities and0−πtransitions in superconducting-magnetic hybrid structures

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