Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

Alidoust, Mohammad; Halterman, Klaus; Valls, Oriol T.

doi:10.1103/physrevb.92.014508

Cited by 66 publications

(55 citation statements)

References 60 publications

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“…Although OTE s-wave pairing has been discussed in diffusive ferromagnet (DF)/conventional spin-singlet swave superconductor junctions, it is difficult to realize pure OTE s-wave pairing state in a DF [60][61][62][63][64][65][66][67][68][69][70][71]. Conversely, the demonstrated anomalous proximity effect generated by ZESABSs specific to unconventional superconductors is remarkable, as it can induce a purely odd-frequency pairing or at least a significant amount of it at low energy.…”

Section: Introductionmentioning

confidence: 99%

Theory of the proximity effect in two-dimensional unconventional superconductors with Rashba spin-orbit interaction

Tamura

Tanaka

2019

Phys. Rev. B

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We study the anomalous proximity effect in diffusive normal metal (DN)/unconventional superconductor junctions, where the local density of states (LDOS) in the DN has a zero-energy peak due to the penetration of the odd-frequency spin-triplet s-wave pairing. In this study, we consider a two-dimensional unconventional superconductor on the substrate in the presence of a Rashba spinorbit coupling (RSOC) λ, where the Rashba vector is parallel to the z-direction. The anomalous proximity effect, originally predicted in spin-triplet p-wave superconductor junctions, is sensitive to the RSOC. It disappears with the increase of λ. On the other hand, the anomalous proximity effect can be switched on by the large λ values in the spin-singlet dxy-wave superconductor junctions. The resulting zero-energy LDOS and the magnitude of the odd-frequency spin-triplet s-wave pair amplitude increase with the increase of λ.

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Section: Introductionmentioning

confidence: 99%

Theory of the proximity effect in two-dimensional unconventional superconductors with Rashba spin-orbit interaction

Tamura

Tanaka

2019

Phys. Rev. B

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“…If differing ferromagnetic materials, constituting the left and right F layers are chosen properly, they respond to an external magnetic field in different ways, providing active control of the magnetization misalignment angles through variations in the intensity and direction of an external magnetic field. It was shown that the superconducting transition temperature [46][47][48][49][50] and density of states 13,[51][52][53][54] reveal prominent signatures of the long-ranged spin-triplet superconductivity 5 as a function of magnetization misalignment. Nevertheless, a direct and clear observation of the equal-spin triplet pairings in superconducting hybrids is still elusive.…”

Section: Introductionmentioning

confidence: 99%

Half-metallic superconducting triplet spin multivalves

Alidoust

Halterman

2018

Phys. Rev. B

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We study spin switching effects in finite-size superconducting multivalve structures. We examine F 1 F 2 SF 3 and F 1 F 2 SF 3 F 4 hybrids where a singlet superconductor (S) layer is sandwiched among ferromagnet (F) layers with differing thicknesses and magnetization orientations. Our results reveal a considerable number of experimentally viable spin valve configurations that lead to on-off switching of the superconducting state. For S widths on the order of the superconducting coherence length ξ 0 , non-collinear magnetization orientations in adjacent F layers with multiple spin-axes leads to a rich variety of triplet spin-valve effects. Motivated by recent experiments, we focus on samples where magnetizations in the F 1 and F 4 layers exist in a fully spin-polarized half metallic phase, and calculate the superconducting transition temperature, spatially and energy resolved density of states, and the spin-singlet and spin-triplet superconducting correlations. Our findings demonstrate that superconductivity in these devices can be completely switched on or off over a wide range of magnetization misalignment angles due to the generation of equal-spin and opposite-spin triplet pairings.

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“…Nearly zero energy states (ZES) are not necessarily MBS. For example, Andreev bounds states can also occur at zero energy [13,[27][28][29][62][63][64][65][66][67]. Here ZES denote any states with (nearly) zero energy, being MBS or not and are related to the well-known zero bias conductance peak [11,12].…”

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confidence: 99%

Tunable magnetic textures in spin valves: From spintronics to Majorana bound states

et al. 2019

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Spin-valve structures in which a change of magnetic configuration is responsible for magnetoresistance led to impressive advances in spintronics, focusing on magnetically storing and sensing information. However, this mature technology also offers versatile control of magnetic textures with usually neglected underlying fringing fields to enable entirely different applications by realizing topologically-nontrivial states. Together with proximity-induced superconductivity in a two-dimensional electron gas with a large g-factor, these fringing fields realized in commercially-available spin valves provide Zeeman splitting, synthetic spin-orbit coupling, and confinement, needed for Majorana bound states (MBS). Detailed support for the existence and control of MBS is obtained by combining accurate micromagnetic simulation of fringing fields used as an input in Bogoliubov de Gennes equation to calculate low-energy spectrum, wavefunction localization, and local charge neutrality. A generalized condition for a quantum phase transition in these structures provides valuable guidance for the MBS evolution and implementing reconfigurable effective topological wires.

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Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

Cited by 66 publications

References 60 publications

Theory of the proximity effect in two-dimensional unconventional superconductors with Rashba spin-orbit interaction

Theory of the proximity effect in two-dimensional unconventional superconductors with Rashba spin-orbit interaction

Half-metallic superconducting triplet spin multivalves

Tunable magnetic textures in spin valves: From spintronics to Majorana bound states

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