Long range triplet Josephson current and 0−π transitions in tunable domain walls
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| Anzahl der Teile | 49 | |
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| Lizenz | CC-Namensnennung 3.0 Unported: Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen. | |
| Identifikatoren | 10.5446/38725 (DOI) | |
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16
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VideotechnikJosephson-KontaktGleitlagerElementarteilchenphysikSupraleiterProfilwalzen
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SupraleiterMaterialProfilwalzenComputeranimation
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SupraleiterMaterialKlangeffektComputeranimation
00:21
ChirpTheodolitElektronisches BauelementMetallschichtMagnetisierungAbstandsmessungKlangeffektProfil <Bauelement>WärmeaustauscherComputeranimation
00:48
Elektrische StromdichteWärmeaustauscherMessungExplorer <Satellit>SpantBlatt <Papier>FrühjahrTechnische ZeichnungDiagramm
00:59
GleichstromFrühjahrDomäne <Kristallographie>Profil <Bauelement>WärmeaustauscherMagnetisierungFerromagnetismusMagnetPatrone <Munition>Technische ZeichnungDiagramm
01:33
Domäne <Kristallographie>KlangeffektProximity-EffektElektronisches BauelementWärmeaustauscherFrühjahrElektrische StromdichteVideotechnikMagnetisierungTechnische ZeichnungDiagramm
02:29
TheodolitElektronenröhreGleichstromElektronisches BauelementSupraleiterDrachenpunktBlatt <Papier>SpinNetzwerkanalyseVideotechnikSatz <Drucktechnik>WärmeaustauscherFerromagnetismusElektrische StromdichteRauschzahlFrühjahrKlangeffektHochsetzstellerTechnische ZeichnungDiagramm
03:53
Differentielles MikrowellenradiometerTemperaturBlatt <Papier>ComputeranimationBesprechung/Interview
Transkript: Englisch(automatisch erzeugt)
00:03
Electrons inside of a superconductor form Cooper pairs. If another material is placed near the superconductor, the whole system becomes superconducting by proximity. Many interesting effects may be seen if that material is ferromagnetic, as a singlet-Cooper pair will acquire an orbital angular momentum
00:23
and transition to a triplet via the foldy-ferrol-Larkin-Ovchinikov effect, or breaking the exchange field. If the magnetization profile is inhomogeneous, then the triplet may have a component protected from the magnetization by symmetry and propagate over long distances through the magnet as though it were a normal metal.
00:45
This is called the long-range triplet component of the order parameter. In this paper, we studied the Josephson current through a tunable exchange spring, which may be of interest for measurement and applications, but also allows us to explore new physics. An exchange spring is constructed from two ferromagnets that are magnetically linked.
01:05
At zero field, the magnetization profile is homogeneous. Applying an external magnetic field induces a partial domain wall, which may be wound up or down until the field is sufficiently large to return to the homogeneous configuration, but in the opposite direction.
01:24
The tunable, reversible, spring-like nature of the magnetization is why the magnet is called an exchange spring. We suggest two realistic exchange springs to study the effects of the domain wall on the Josephson current.
01:40
The first is a wide cobalt-permaloi system. We display the current as a function of the twist, delta-phi, of the domain wall. As the twist is increased along the x-axis, the measurable current increases, shown as a solid line. The appearance of the current is attributable to the long-range triplet component
02:01
that increases with increasing twist of the domain wall. Noteworthy is also the presence of a finite singlet contribution to the current, shown as a dashed line, despite the very wide magnetic system considered here. This is due to the cascading proximity effect in a continuously rotating magnetization. The inset shows that as one increases the thickness of the exchange spring,
02:25
the current decreases since the domain wall edges flatten. A second system, nickel-3-manganese-nickel, is much softer than the previous cobalt-permaloi, which introduces a sizable singlet current across the system, again shown as a dashed line.
02:42
We are drawn to the curious consequence of this, a zero-pi transition shown as a V-shaped solid line. The system is too wide for the Budsten-Bulewski-type transition measured in homogeneous films to appear here. Further, the zero-pi transition presented in a paper on the spin valve by Hussey and Budsten
03:02
cannot apply here either since the singlet contribution is negligible in a spin valve system of similar thickness. What we see here is a new type of zero-pi transition. The long-ranged triplet components always drive the current in one direction that we call negative by convention.
03:20
The singlet contribution to the current from the superconductor is also present due to the weakness of the ferromagnet and modified by the cascade effect. The thickness of the layer is chosen so that the singlet contribution to the current is in the positive direction in this sample. At the point where the singlet counterbalances the other components,
03:42
no current is measured. Contrastingly, the inset figure shows the node disappears if we increase the thickness of the exchange spring, changing the direction of the singlet pairs. Suggestions are made for realizing the experiments proposed in the paper and the temperature dependence is discussed.
04:01
Thank you very much for listening.
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