Robustness of Spin-Triplet Pairing and Singlet–Triplet Pairing Crossover in Superconductor/Ferromagnet Hybrids

Kawabata, Shiro; Asano, Yasuhiro; Tanaka, Yukio; Golubov, A. A.

doi:10.7566/jpsj.82.124702

Cited by 29 publications

(32 citation statements)

References 108 publications

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“…The damped oscillatory behavior of the pair correlations can lead to spectroscopic signatures in the form of DOS inversions, 58 and multiple oscillations. 24 In the quasiclassical approximation, 35,38,55,56 a ZEP can emerge from the long-range triplet correlations 33,59 in SF F systems. However, this approximation is not appropriate for experimental conditions involving strong magnets and clean interfaces.…”

Section: Local Density Of Statesmentioning

confidence: 99%

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

2015

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Using a self-consistent Bogoliubov-de Gennes approach, we theoretically study the proximity-induced density of states (DOS) in clean SF F spin-valves with noncollinear exchange fields. Our results clearly demonstrate a direct correlation between the presence of a zero energy peak (ZEP) in the DOS spectrum and the persistence of spin-1 triplet pair correlations. By systematically varying the geometrical and material parameters governing the spin-valve, we point out to experimentally optimal system configurations where the ZEPs are most pronounced, and which can be effectively probed via scanning tunneling microscopy. We complement these findings in the ballistic regime by employing the Usadel formalism in the full proximity limit to investigate their diffusive SF F counterparts. We determine the optimal normalized ferromagnetic layer thicknesses which result in the largest ZEPs. Our results can serve as guidelines in designing samples for future experiments.

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Section: Local Density Of Statesmentioning

confidence: 99%

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

2015

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“…The θ independent part of the magnetization, i.e., M I y (d) and M I z (d), is due to the proximity effect common in S/F junctions, similar to the one inducing the STCs in F /S/F and S/F /F junctions [39,40,42,45,51,54].…”

Section: Induced Magnetization In Normal Metalmentioning

confidence: 99%

“…On the contrary, when the magnetization in the F is non-uniform in a S/F junction, the STC formed by electrons of equal spin (|S z | = 1) can also be induced in the F. This includes cases, for instance, where the F contains a magnetic domain wall [30][31][32][33][34][35][36], the junction consists of F multilayers [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55], the interface of S/F junction is spin active [56][57][58][59][60][61], and the ferromagnetic resonance occurs [62][63][64]. Although the pair amplitude of STC with |S z | = 1 monotonically decreases with increasing the thickness of F, the STC with |S z | = 1 can propagate into the F over a distance of the order of ξ 0 = D F /2πk B T (T : temperature), which is typically about several dozen nanometers [65].…”

Section: Introductionmentioning

confidence: 99%

Magnetization induced by odd-frequency spin-triplet Cooper pairs in a Josephson junction with metallic trilayers

Hikino

Yunoki

2015

Phys. Rev. B

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We theoretically study the magnetization inside a normal metal induced in an s-wave superconductor/ferromagnetic metal/normal metal/ferromagnetic metal/s-wave superconductor (S/F1/N/F2/S) Josephson junction. Using the quasiclassical Green's function method, we show that the magnetization becomes finite inside the N . The origin of this magnetization is due to odd-frequency spin-triplet Cooper pairs formed by electrons of equal and opposite spins, which are induced by the proximity effect in the S/F1/N/F2/S junction. We find that the magnetiza-, where θ is the superconducting phase difference between the two Ss and d is the thickness of N . The θ independent magnetization M I (d) exists generally in S/F junctions, while M II (d, θ) carries all θ dependence and represents the fingerprint of the phase coherence between the two Ss in Josephson junctions. The θ dependence thus allows us to control the magnetization in the N by tuning θ for a fixed d. We show that the θ independent magnetization M I (d) weakly decreases with increasing d, while the θ dependent magnetization M II (d, θ) rapidly decays with d. Moreover, we find that the time-averaged magnetization M II (d, θ) exhibits a discontinuous peak at each resonance DC voltage Vn = n ωS/2e (n: integer) when DC voltage V as well as AC voltage vac(t) with frequency ωS are both applied to the S/F1/N/F2/S junction. This is because M II (d, θ) oscillates generally in time t (AC magnetization) with dθ/dt = 2e[V + vac(t)]/ and thus M II (d, θ) = 0, but can be converted into the time-independent DC magnetization for the DC voltage at Vn. We also discuss that the magnetization induced in the N can be measurably large in realistic systems. Therefore, the measurement of the induced magnetization serves as an alternative way to detect the phase coherence between the two Ss in Josephson junctions. Our results also provide a basic concept for tunable magnetization in superconducting spintronics devices.

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“…Without SO coupling, this typically occurs for exchange fields fulfilling the resonant condition 28,29 h ∼ E g , where E g is the minigap energy. However, the mechanism for the enhanced density of states due to triplets in the present work is fundamentally different from previous literature as it originates from a parity effect due to SO coupling which is present independently on the exact junction parameters.…”

Section: Theorymentioning

confidence: 99%

Giant triplet proximity effect inπ-biased Josephson junctions with spin-orbit coupling

Jacobsen

Linder

2015

Phys. Rev. B

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In diffusive Josephson junctions the phase-difference φ between the superconductors strongly influences the spectroscopic features of the layer separating them. The observation of a uniform minigap and its phase modulation were only recently experimentally reported, demonstrating agreement with theoretical predictions up to now -a vanishing minigap at φ = π. Remarkably, we find that in the presence of intrinsic spin-orbit coupling a giant proximity effect due to spin-triplet Cooper pairs can develop at φ = π, in complete contrast to the suppressed proximity effect without spin-orbit coupling. We here report a combined numerical and analytical study of this effect, proving its presence solely based on symmetry arguments, which makes it independent of the specific parameters used in experiments. We show that the spectroscopic signature of the triplets is present throughout the entire ferromagnetic layer. Our finding offers a new way to artificially create, control and isolate spin-triplet superconductivity.

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Robustness of Spin-Triplet Pairing and Singlet–Triplet Pairing Crossover in Superconductor/Ferromagnet Hybrids

Cited by 29 publications

References 108 publications

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

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

Magnetization induced by odd-frequency spin-triplet Cooper pairs in a Josephson junction with metallic trilayers

Giant triplet proximity effect inπ-biased Josephson junctions with spin-orbit coupling

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