Spin transfer torque and exchange coupling in Josephson junctions with ferromagnetic superconductor reservoirs

Shomali, Zahra; Asgari, Reza

doi:10.1088/1361-648x/ab4b1d

Cited by 5 publications

(5 citation statements)

References 71 publications

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“…This numerical approach has also found excellent agreement with results that rely on asymptotic approximations, such as the Andreev approximation [59], ab initio calculations [58], and supports the half-metallic phase where the magnetization strength is as large as the Fermi level [29,30,36]. This latter phase is inaccessible to approximate methods, such as the quasiclassical approach, which considers the Fermi level to be the largest energy in the system [20,21,38,[54][55][56].…”

Section: Introductionsupporting

confidence: 61%

Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

Halterman,

Alidoust,

Smith

et al. 2021

Preprint

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We consider a Josephson junction with F 1 F 2 F 3 ferromagnetic trilayers in the ballistic regime, where the magnetization in each ferromagnet F i (i = 1, 2, 3), can have arbitrary orientations and magnetization strengths. The trilayers are sandwiched between two s-wave superconductors with a macroscopic phase difference ∆ϕ. With our generalised theoretical and numerical techniques, we are able to study the planar spatial profiles and ∆ϕdependencies of the charge supercurrents, spin supercurrents, spin torques, and density of states for complex systems that are finite in two dimensions. A broad range of magnetization strengths of the central F 2 layer are considered, from an unpolarized normal metal (N) to a half-metallic phase, supporting only one spin species. Our results reveal that when the magnetization configuration in F 1 F 2 F 3 has three orthogonal components, a supercurrent can flow at ∆ϕ = 0, and a strong second harmonic in the current-phase relation appears. Remarkably, upon increasing the magnetization strength in the central ferromagnet layer up to the half-metallic limit, the self-biased current and second harmonic component become dramatically enhanced, and the critical supercurrent reaches its maximum value. The higher harmonics in the current-phase relations can be controlled by the relative magnetization orientations, with negligible current damping compared to the corresponding F 1 N F 3 counterparts. Additionally, for a broad range of exchange field strengths in the central ferromagnet F 2 , the ground state of the system can be tuned to an arbitrary phase difference ϕ 0 , e.g., by rotating the magnetization in the outer ferromagnet F 3 . For intermediate exchange field strengths in F 2 , a ϕ 0 state can arise that creates a superconducting diode effect, whereby ∆ϕ can be tuned to create a one-way dissipationless current flow. The spatial maps of the spin currents and effective magnetic moments reveal a long-ranged spin torque in the halfmetallic phase. Moreover, the density of states studies demonstrate the emergence of zero energy peaks for the mutually orthogonal magnetization configurations, which is strongest in the half-metallic phase. Our results suggest that this simple trilayer Josephson junction can be an excellent candidate for producing experimentally accessible signatures for long-ranged self-biased supercurrents, and supercurrent diode-effects.

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Section: Introductionsupporting

confidence: 61%

Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

Halterman,

Alidoust,

Smith

et al. 2021

Preprint

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“…F = E F . The wave functions are found by solving the matrix equation ( 1) and are presented in the following [13]. Hence, the total wave function in the non-superconducting region is written as,…”

Section: Model and Basic Equationsmentioning

confidence: 99%

“…Considering this condition, the ABS with E ⩽ |∆ ↑,↓ | have the dominant contribution seeking the transport properties in investigated FS 1 |SOC|N|FS 2 system. The STT is then calculated, contemplating only the ABSs [13].…”

Section: Model and Basic Equationsmentioning

confidence: 99%

“…The Josephson contacts containing FS reservoirs have not been widely studied. To the best of our knowledge, limited studies dealing with calculating spin transfer torque (STT) in short contacts of FS 1 |N|FS 2 have been performed [12,13]. As mentioned before, recently, many researches have been devoted to the STT deportment in Josephson structures with FS reservoirs.…”

Section: Introductionmentioning

confidence: 99%

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Josephson junctions with chiral p-wave ferromagnetic superconductor reservoirs in presence of spin-orbit coupling interaction

Shomali¹

2022

Supercond. Sci. Technol.

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The spin transfer torque (STT), is studied in new cases of Josephson junctions containing triplet p-wave chiral ferromagnetic superconductor reservoirs (FS). To be more precise, FS$_1$|spin orbit coupling layer (SOC$_1$)|Normal metal (N)|SOC$_2$|FS$_2$ materials have been investigated. Specifically, FS$_1$|N|FS$_2$ structure with one layer of SOC at FS$_1$|N interface and also two layers of SOC at both FS$_1$|N and N|FS$_2$ interfaces are investigated. For the structures including two SOC layers, both symmetric and asymmetric cases with respectively equal and different potential strengths are studied. The ballistic Josephson junctions are studied solving the Bogoliubov-de-Gennes equation. In particular, the cases with short normal metal contacts with thickness much smaller than the superconducting coherence length, $\psi$, are studied. It is obtained for the case with only one SOC layer, while the absolute value of the out-of-plane STT remains almost unchanged, its direction reverses for lower values of $\alpha$, the angle between exchange fields of the two ferromagnetic superconductors. Also, the nanosystem in presence of two similar SOCs, exhibits lower out-of-plane STT. This is justified as the unit vector along the interface normal for the SOC$_1$ is in the opposite direction of the second SOC$_2$ layer. Hence, one can expect that these potentials fade the effect of each other. When the SOCs are not the same and have different values of potential strength, the out-of-plane STT reduces less which is attributed to slighter cancellation due to unequal potential strength. Moreover, the barrier strength is varied. It has been shown that the barrier strength increment changes the behavior of the STT. Particularly, it is found that it results in sign and value change of the STT. Further, the emergence of in-plane STTs in presence of SOC are confirmed and investigated for various systems.

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“…Heat dissipation due to electric resistance is one of the most critical issues in spintronics. The dissipationless current in superconductors in combination with ferromagnets proposes new types of devices to manipulate spin and charge currents [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Anisotropic angle-dependent Andreev reflection at the ferromagnet/superconductor junction on the surface of topological insulators

Salehi

2023

Phys. Scr.

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We theoretically demonstrate that a ferromagnetic/superconductor junction on the surface of three-dimensional topological insulators (3D TIs) has an anisotropic angle-dependent Andreev reflection when the in-plane magnetization has a component perpendicular to the junction. In the presence of in-plane magnetization, the Dirac cone’s location adjusts in the k-space, whereas its out-of-plane component induces a gap. This movement leads to the anisotropic angle-dependent Andreev reflection and creates transverse conductance flows parallel to the interface. Also, an indirect gap induces in the junction, which removes the transport signatures of Majorana bound states. Because of the full spin-momentum locking of Dirac fermions on the surface of 3DTIs, a torque called Andreev Transfer Torque (ATT) imposes on the junction. Moreover, we propose a setup to detect them experimentally.

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Spin transfer torque and exchange coupling in Josephson junctions with ferromagnetic superconductor reservoirs

Cited by 5 publications

References 71 publications

Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

Josephson junctions with chiral p-wave ferromagnetic superconductor reservoirs in presence of spin-orbit coupling interaction

Anisotropic angle-dependent Andreev reflection at the ferromagnet/superconductor junction on the surface of topological insulators

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