Coexistence of superconductivity and spin-splitting fields in superconductor/ferromagnetic insulator bilayers of arbitrary thickness

Hijano, Alberto; Ilić, Stefan; Rouco, Mikel; González-Orellana, Carmen; Ilyn, M.; Rogero, Celia; Virtanen, Pauli; Heikkilä, Tero T.; Khorshidian, S.; Spies, M.; Ligato, Nadia; Giazotto, Francesco; Strambini, Elia; Bergeret, F. S.

doi:10.1103/physrevresearch.3.023131

Cited by 31 publications

(37 citation statements)

References 55 publications

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“…Majorana zero modes emerge localised at the edges of the FM, due to the synergy between the externally applied supercurrents with the emergent in the SCs exchange fields [27]. We remark that several works have demonstrated both theoretically [28,29] and experimentally [30][31][32] the emergence of exchange fields in conventional SCs proximised by FIs. Moreover, developments in the fabrication of SC-FI heterostructures [33] and ferromagnetic metallic nanonwires embedded in conventional SCs [34][35][36], enhance the experimental feasibility of the proposed platform.…”

Section: A Novel Platformmentioning

confidence: 76%

Majorana Zero Modes in Ferromagnetic Wires without Spin-Orbit Coupling

2021

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We present a novel controllable platform for engineering Majorana zero modes. The platform consists of a ferromagnetic metallic wire placed among conventional superconductors, which are in proximity to ferromagnetic insulators. We demonstrate that Majorana zero modes emerge localised at the edges of the ferromagnetic wire, due to the interplay of the applied supercurrents and the induced by proximity exchange fields with conventional superconductivity. Our mechanism does not rely on the pairing of helical fermions by combining conventional superconductivity with spin-orbit coupling, but rather exploits the misalignment between the magnetization of the ferromagnetic insulators and that of the ferromagnetic wire.

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Section: A Novel Platformmentioning

confidence: 76%

Majorana Zero Modes in Ferromagnetic Wires without Spin-Orbit Coupling

2021

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“…A diffusive superconducting film is placed on top of a FI film. A typical example is Eu/Al studied in several papers [2,4,5,7,24]. In these systems, the EuS film is polycrystalline and magnetic domains with sharp boundaries are very common, in particular before the first magnetization of the EuS [4].…”

Section: The Modelmentioning

confidence: 99%

Quasiparticle density of states and triplet correlations in superconductor/ferromagnetic-insulator structures across a sharp domain wall

Hijano,

Golovach,

Bergeret

2022

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A ferromagnetic insulator (FI) in contact with a superconductor (S) is known to induce a spin splitting of the BCS density of states at the FI/S interface. This spin splitting causes the Cooper pairs to reduce their singlet-state correlations and acquire odd-in-frequency triplet correlations. We consider a diffusive FI/S bilayer with a sharp magnetic domain wall in the FI and study the local quasiparticle density of states and triplet superconducting correlations. In the case of collinear alignment of the domains, we obtain analytical results by solving the Usadel equation. For a small enough exchange field, we also find an analytical expression for arbitrary magnetic textures, which reveals how the triplet component vector depends on the local magnetization of the FI. For an arbitrary angle between the magnetizations and the strength of the exchange field, we numerically solve the problem of a sharp domain wall. We finally propose two different setups based on FI/S/F stacks, where F is a ferromagnetic layer, to filter out singlet pairs and detect the presence of triplet correlations via tunneling differential conductance measurements.

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“…First, magnetization dynamics results in the energy current [4,47] 2 , where α is the contribution to the Gilbert damping coefficient due to the contact. Second, in superconductors the spin splitting in the Bogoliubov spectrum generated by FI through the magnetic proximity effect [20,23,48,49] leads to the strong coupling between energy and spin degrees of freedom [23]. The mechanism of converting pumped quasiparticle energy to spin accumulation via elastic spin-relaxation processes is demonstrated in Fig.…”

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confidence: 98%

“…For YIG [64], m M ≈ 1 eV −1 Å −2 and [65] v s ≈ 500 Å 3 . Figure 4 shows S(T ) for parameters qualitatively corresponding to the EuS/Al and YIG/Nb based FI/SC bilayers that have been studied recently [34,49]. The spin signals are enhanced even more due to the energy dependence of the inelastic scattering rate when the relaxation is due to the electron-phonon coupling.…”

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confidence: 99%

Giant enhancement to spin battery effect in superconductor/ferromagnetic insulator systems

et al. 2021

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We develop a theory of the spin battery effect in superconductor/ferromagnetic insulator (SC/FI) systems taking into account the magnetic proximity effect. We demonstrate that the spin-energy mixing enabled by the superconductivity leads to the enhancement of spin accumulation by several orders of magnitude relative to the normal state. This finding can explain the recently observed giant inverse spin Hall effect generated by thermal magnons in the SC/FI system. We suggest a nonlocal electrical detection scheme which can directly probe the spin accumulation driven by the magnetization dynamics. We predict a giant Seebeck effect converting the magnon temperature bias into the nonlocal voltage signal. We also show how this can be used to enhance the sensitivity of magnon detection even up to the single-magnon level.

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Coexistence of superconductivity and spin-splitting fields in superconductor/ferromagnetic insulator bilayers of arbitrary thickness

Cited by 31 publications

References 55 publications

Majorana Zero Modes in Ferromagnetic Wires without Spin-Orbit Coupling

Majorana Zero Modes in Ferromagnetic Wires without Spin-Orbit Coupling

Quasiparticle density of states and triplet correlations in superconductor/ferromagnetic-insulator structures across a sharp domain wall

Giant enhancement to spin battery effect in superconductor/ferromagnetic insulator systems

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