Zero phase difference supercurrent in ferromagnetic Josephson junctions

Margaris, I; Paltoglou, Vassilis; Flytzanis, N.

doi:10.1088/0953-8984/22/44/445701

Cited by 40 publications

(44 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The second condition contradicts the results based on the Bogolubov-de Gennes calculations [33], which yield I an = 0 for any noncoplanar spin texture, including the case when h ⊥ P l,r . To get agreement with those results one has to take into account the magnetic proximity effect [53][54][55][56] that induces an effective exchange field b r and b l in the superconducting electrodes [ Fig.…”

Section: Spin-filtering Boundary Conditions Beyond the Quasiclascontrasting

confidence: 58%

“…For any coplanar magnetization distribution there exists a global SU(2) spin rotation that flips the direction of M, and the condition (3) is fulfilled. For this reason, the AJE requires a noncoplanar magnetization texture as predicted for ballistic S/F/F/F/S systems [32][33][34]. The anomalous current obtained in those works shows rapid oscillations as a function of the ferromagnetic thickness.…”

Section: Introductionmentioning

confidence: 87%

“…By combining this extra symmetry with the general time-reversal symmetry, j (ϕ,h) = − j (−ϕ, − h), one obtains that j (ϕ) = − j (−ϕ), and hence within the quasiclassical approach, the AJE cannot take place for any spatial dependence of the exchange field h(r). However, we know from previous works that anomalous current may be generated at least in ballistic S/F/S junctions with noncoplanar configuration of the magnetization [32][33][34]. What is the origin of the apparent contradiction between the explicit ballistic calculations in those references and the magnetization reversal symmetry of the Usadel equation?…”

Section: Quasiclassical Symmetry Of the Charge Currentmentioning

confidence: 98%

“…1(a). Here FI stands for the spin-filtering barriers with magnetizations P r,l , and F is the monodomain weak ferromagnet with exchange field h. From previous works [32][33][34] one would expect the anomalous current to be proportional to the spin chirality χ = h · ( P r × P l ). However, such a term does not satisfy the symmetry (10) because the sign of χ changes when h → −h.…”

Section: Spin-filtering Boundary Conditions Beyond the Quasiclasmentioning

confidence: 99%

See 3 more Smart Citations

Anomalous current in diffusive ferromagnetic Josephson junctions

2017

View full text Add to dashboard Cite

We demonstrate that in diffusive superconductor/ferromagnet/superconductor (S/F/S) junctions a finite, anomalous Josephson current can flow even at zero phase difference between the S electrodes. The conditions for the observation of this effect are noncoplanar magnetization distribution and a broken magnetization inversion symmetry of the superconducting current. The latter symmetry is intrinsic for the widely used quasiclassical approximation and prevented previous works based on this approximation from obtaining the Josephson anomalous current. We show that this symmetry can be removed by introducing spin-dependent boundary conditions for the quasiclassical equations at the superconducting/ferromagnet interfaces in diffusive systems. Using this recipe, we consider generic multilayer magnetic systems and determine the ideal experimental conditions in order to maximize the anomalous current.

show abstract

Section: Spin-filtering Boundary Conditions Beyond the Quasiclascontrasting

confidence: 58%

Section: Introductionmentioning

confidence: 87%

Section: Quasiclassical Symmetry Of the Charge Currentmentioning

confidence: 98%

Section: Spin-filtering Boundary Conditions Beyond the Quasiclasmentioning

confidence: 99%

See 2 more Smart Citations

Anomalous current in diffusive ferromagnetic Josephson junctions

2017

View full text Add to dashboard Cite

show abstract

“…Such a junction then supplies a phase shift ϕ in analogy to how a voltage is supplied by a battery, with the important difference that the phase does not discharge since the superconducting currents flowing in the system are dissipationless. In junctions that effectively feature three ferromagnetic layers with misaligned magnetizations, the spin chirality χ has been demonstrated [102,103] to be intimately linked with the realization of a ϕ state: χ ≡ M 1 · (M 2 × M 3). However, the ϕ-junction may also be realized in other geometries and with homogeneous Zeeman fields in the presence of spin-orbit coupling, as predicted in Ref.…”

Section: Phase-batteries and Thermoelectric Effectsmentioning

confidence: 99%

Superconducting spintronics

2015

View full text Add to dashboard Cite

Traditional studies that combine spintronics and superconductivity have mainly focused on the injection of spin-polarized quasiparticles into superconducting materials. However, a complete synergy between superconducting and magnetic orders turns out to be possible through the creation of spin-triplet Cooper pairs, which are generated at carefully engineered superconductor interfaces with ferromagnetic materials. Currently, there is intense activity focused on identifying materials combinations that merge superconductivity and spintronics to enhance device functionality and performance. The results look promising: it has been shown, for example, that superconducting order can greatly enhance central effects in spintronics such as spin injection and magnetoresistance. Here, we review the experimental and theoretical advances in this field and provide an outlook for upcoming challenges in superconducting spintronics.At the interface between materials with radically different properties, new physical phenomena can emerge. A classical example of such an interface is that between a superconductor and a ferromagnet where the opposing electron orders destructively interfere; however, it turns out that under the right conditions at a superconductorferromagnet interface both superconductivity and spin-polarization can unite to create a new superconducting state that offers tantalizing possibilities for spin transport in which Joule heating and dissipation are minimized.Spintronics offers the potential for creating circuits in which logic operations controlled by spin currents can be performed faster and more energy efficient [1] than the charge-based equivalent in semiconductor transistor technologies. Spintronics is one of the most active areas of research and while it offers control of spin and charge at the nanometer scale, it has also found sensory applications in hard disk drive read heads via the giant magnetoresistance effect [2,3]. The idea of combining superconductivity with spintronics has historically focused on the net spin-polarization of quasiparticles in superconductors. It is interesting to note that the first spin transport experiments [4-6] involved ferromagnet-superconductor bilayers and predated non-superconducting spin transport experiments [8]. As will be discussed in this review, it is possible to create pseudo-chargeless spin-1/2 excitations in superconductors [7] which have extremely long spin lifetimes.Recently, a more complete synergy between superconductivity and spintronics has been made possible through the discovery of spin-triplet Cooper pairs at superconductor-ferromagnet interfaces. Non-superconducting spin currents are generated by passing charge currents through ferromagnetic materials. As will be explained in this review, spin currents can also be generated by passing supercurrents through ferromagnetic materials. Charge flow within superconductors is carried by Cooper pairs which consist of interacting pairs of electrons [9]. The idea of combining superconducting and magnetic order wa...

show abstract

Pt and CoB trilayer Josephson $$\pi $$ junctions with perpendicular magnetic anisotropy

Satchell

Mitchell

Shepley

et al. 2021

Sci Rep

View full text Add to dashboard Cite

We report on the electrical transport properties of Nb based Josephson junctions with Pt/Co$$_{68}$$ 68 B$$_{32}$$ 32 /Pt ferromagnetic barriers. The barriers exhibit perpendicular magnetic anisotropy, which has the main advantage for potential applications over magnetisation in-plane systems of not affecting the Fraunhofer response of the junction. In addition, we report that there is no magnetic dead layer at the Pt/Co$$_{68}$$ 68 B$$_{32}$$ 32 interfaces, allowing us to study barriers with ultra-thin Co$$_{68}$$ 68 B$$_{32}$$ 32 . In the junctions, we observe that the magnitude of the critical current oscillates with increasing thickness of the Co$$_{68}$$ 68 B$$_{32}$$ 32 strong ferromagnetic alloy layer. The oscillations are attributed to the ground state phase difference across the junctions being modified from zero to $$\pi $$ π . The multiple oscillations in the thickness range $$0.2~\leqslant ~d_\text {CoB}~\leqslant ~1.4$$ 0.2 ⩽ d CoB ⩽ 1.4 nm suggests that we have access to the first zero-$$\pi $$ π and $$\pi $$ π -zero phase transitions. Our results fuel the development of low-temperature memory devices based on ferromagnetic Josephson junctions.

show abstract

Zero phase difference supercurrent in ferromagnetic Josephson junctions

Cited by 40 publications

References 31 publications

Anomalous current in diffusive ferromagnetic Josephson junctions

Anomalous current in diffusive ferromagnetic Josephson junctions

Superconducting spintronics

Pt and CoB trilayer Josephson $$\pi $$ junctions with perpendicular magnetic anisotropy

Contact Info

Product

Resources

About