Electrical and thermal generation of spin currents by magnetic bilayer graphene

Ghiasi, Talieh S.; Kaverzin, Alexey; Dismukes, Avalon H.; Wal, Dennis K. de; Roy, Xavier; Wees, B. J. van

doi:10.1038/s41565-021-00887-3

Cited by 107 publications

(137 citation statements)

References 55 publications

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“…Our work also points out that hydrostatic pressure can be generally used to change the interlayer distance up to a remarkable 10%, which provides a new way to boost proximity effects in van der Waals heterstructures, e.g. exchange interaction induced into graphene [47][48][49][50], or into TDMCs [51,52], furthermore, a strong proximity effect on correlated magic angle twistronics devices [53,54], or to stabilize fragile states like the topological insulator phase in graphene-TDMC heterostructures [33].…”

mentioning

confidence: 88%

Boosting proximity spin orbit coupling in graphene/WSe$_2$ heterostructures via hydrostatic pressure

Fülöp,

Márffy,

Zihlmann

et al. 2021

Preprint

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Van der Waals heterostructures composed of multiple few layer crystals allow the engineering of novel materials with predefined properties. As an example, coupling graphene weakly to materials with large spin orbit coupling (SOC) allows to engineer a sizeable SOC in graphene via proximity effects. The strength of the proximity effect depends on the overlap of the atomic orbitals, therefore, changing the interlayer distance via hydrostatic pressure can be utilized to enhance the interlayer coupling between the layers. In this work, we report measurements on a graphene/WSe2 heterostructure exposed to increasing hydrostatic pressure. A clear transition from weak localization to weak anti-localization is visible as the pressure increases, demonstrating the increase of induced SOC in graphene.

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mentioning

confidence: 88%

Boosting proximity spin orbit coupling in graphene/WSe$_2$ heterostructures via hydrostatic pressure

Fülöp,

Márffy,

Zihlmann

et al. 2021

Preprint

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“…In this regime, the YIG-induced IP exchange field (< 1 meV) (14,41) hardly spin-splits the QP DOS of the 2H-NbSe2 and the transition-state enhancement of QP iSHE thus relies mostly on the superconducting-coherence-relevant resonant absorption (14,16,42), (25) and Majorana fermions (26,27). Our findings, together with recent progresses in 2D SCs and magnetic vdW crystals (22,24), open up an avenue for highlyefficient atomically-thin spin-to-charge converters via symmetry engineering.…”

Section: Resultsmentioning

confidence: 65%

Role of Two-Dimensional Ising Superconductivity in the Nonequilibrium Quasiparticle Spin-to-Charge Conversion Efficiency

et al. 2021

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Two-dimensional (2D) superconductors (SCs) with Ising spin-orbit coupling are regarded as a central ingredient for the topological protection of spin-triplet Cooper pairs and, thereby, Majorana fermions. Here, we fabricate non-local magnon devices to examine how such 2D Ising superconductivity affects the conversion efficiency of magnon spin to quasiparticle charge in superconducting flakes of 2H-NbSe 2 transferred onto ferromagnetic insulating Y 3 Fe 5 O 12 . Comparison with a reference device based on a conventionally paired superconductor shows that the Y 3 Fe 5 O 12 -induced exchange spinsplitting in the NbSe 2 flake is hindered by its inherent spin-orbit-field, which, in turn, limits the transition-state enhancement of the spin-to-charge conversion efficiency. Our out-of-equilibrium study highlights the significance of symmetry matching between underlying Cooper pairs and exchange-induced spin-splitting for the giant transitionstate spin-to-charge conversion and may have implications towards proximity-engineered spin-polarized triplet pairing via tuning the relative strength of exchange and spin-orbit fields in ferromagnetic insulator/2D Ising SC bilayers. Ising Cooper pairing governs out-of-equilibrium spin-to-charge conversion characteristics.materials provide new platforms to explore novel physical phenomena in various geometries (22), including van der Waals (vdW) heterostructures with a twist, and in proximity combination with magnetic vdW flakes and/or thin films (23,24). Because excited QPs and Cooper pairs in the superconducting condensate state are intimately correlated (1-6), studies of non-equilibrium QP spin properties in such 2D SCs are of fundamental importance for understanding equilibrium spin-polarized triplet Cooper pairing (1-6) and the possible stabilization of Majorana fermions (25-27). 2D superconductivity has been recently discovered in monolayer transition metal dicalcogenides (TMDs) (17) such as gated 2H-MoS2 (18,19) and 2H-NbSe2 (20). Interestingly, the in-plane (IP) upper critical field 𝜇 0 𝐻 𝑐2 ∥ is found to far exceed the Pauli paramagnetic limit of isotropic Bardeen-Cooper-Schrieffer (BCS) SCs 𝜇 0 𝐻 𝑃 𝐵𝐶𝑆 ≈ 1.84Tc (28), where Tc is the superconducting transition temperature. Such an enhancement of 𝜇 0 𝐻 𝑐2 ∥ is explained by Ising spin-orbit coupling (SOC) (17-21), rooted in the broken IP crystal inversion symmetry plus the large SOC due to heavy transition metal atoms in TMDs. The Ising SO field 𝜇 0 𝐻 𝑆𝑂 (as large as several hundred Tesla in the monolayer limit) (17-21) strongly pins Cooper pair spins at K and K' points of the hexagonal Brillouin zone to opposite out-of-plane (OOP) directions over IP applied magnetic fields. This stabilizes OOP Cooper pairing and forms so-called Ising superconductivity (17-21).We here investigate how the 2D Ising superconductivity influences the transition-state enhancement of magnon spin to QP charge conversion in a superconducting flake of 2H-NbSe2(20,29-31) (Fig. 1A) and compare its efficiency with a conventional superconducting thin film of ...

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“…Several emergent phenomena have been observed in TMDs in heterostructure with magnetic insulators, such as proximity induced magnetoluminescence, coupled spin-valley physics, valley excitonic Zeeman splitting ( Seyler et al., 2018 ; Zhong et al., 2017 , 2020 ). The investigations of magnetic proximity effects with superconductors ( Kezilebieke et al., 2020 ) and graphene ( Ghiasi et al., 2021 ; Karpiak et al., 2019 ) provide prospects of inducing topological superconducting effects and induced magnetism in van der Waals heterostructures. However, spintronic devices with vdW magnets are limited to cryogenic temperatures, inhibiting its broader practical applications.…”

Section: Applicationsmentioning

confidence: 99%

Challenges and opportunities in 2D heterostructures for electronic and optoelectronic devices

et al. 2022

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Electrical and thermal generation of spin currents by magnetic bilayer graphene

Cited by 107 publications

References 55 publications

Boosting proximity spin orbit coupling in graphene/WSe$_2$ heterostructures via hydrostatic pressure

Boosting proximity spin orbit coupling in graphene/WSe$_2$ heterostructures via hydrostatic pressure

Role of Two-Dimensional Ising Superconductivity in the Nonequilibrium Quasiparticle Spin-to-Charge Conversion Efficiency

Challenges and opportunities in 2D heterostructures for electronic and optoelectronic devices

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