Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures

Yang, Bowen; Lohmann, Mark; Barroso, David; Liao, Ingrid; Lin, Zhisheng; Liu, Yawen; Bartels, Ludwig; Watanabe, Kenji; Taniguchi, Takashi; Shi, Jing

doi:10.1103/physrevb.96.041409

Cited by 116 publications

(125 citation statements)

References 38 publications

(57 reference statements)

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“…Previous analyses have concluded that the spin relaxation is dominated by Rashba SOC [25,30], which is seemingly at odds with the presence of giant spin lifetime anisotropy. By reanalyzing the magnetoconductance measurements of Ref.…”

mentioning

confidence: 55%

“…Magnetotransport measurements revealed that graphene in contact with WS 2 exhibits a large weak antilocalization (WAL) peak, revealing a strong SOC induced by proximity effects [24][25][26]30]. Fits to the magnetoconductance yielded spin lifetimes τ s ≈ 5 ps, which is two to three orders of magnitude lower than graphene on traditional substrates [10,31].…”

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confidence: 99%

“…(Ref. [30] in the main text). This analysis is intended to show that the theory of spin lifetime anisotropy presented in this Letter can be consistent with prior measurements of WAL in graphene/TMDC heterostructures.…”

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confidence: 99%

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Giant Spin Lifetime Anisotropy in Graphene Induced by Proximity Effects

et al. 2017

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We report on fundamental aspects of spin dynamics in heterostructures of graphene and transition metal dichalcogenides (TMDCs). By using realistic models derived from first principles we compute the spin lifetime anisotropy, defined as the ratio of lifetimes for spins pointing out of the graphene plane to those pointing in the plane. We find that the anisotropy can reach values of tens to hundreds, which is unprecedented for typical 2D systems with spin-orbit coupling and indicates a qualitatively new regime of spin relaxation. This behavior is mediated by spin-valley locking, which is strongly imprinted onto graphene by TMDCs. Our results indicate that this giant spin lifetime anisotropy can serve as an experimental signature of materials with strong spin-valley locking, including graphene/TMDC heterostructures and TMDCs themselves. Additionally, materials with giant spin lifetime anisotropy can provide an exciting platform for manipulating the valley and spin degrees of freedom, and for designing novel spintronic devices. [3,4], where the combined system might be engineered for specific applications [5] or might enable the exploration of new phenomena [6,7]. In the field of spintronics, graphene has exceptional charge transport properties but weak spin-orbit coupling (SOC) on the order of 10 µeV [8], which makes it ideal for long-distance spin transport [9-11] but ineffective for generating or manipulating spin currents. To advance towards spin manipulation, recent work has focused on heterostructures of graphene and magnetic insulators [12][13][14][15][16] or strong SOC materials such as transition metal dichalcogenides (TMDCs) and topological insulators [17][18][19]. The SOC induced in graphene by a TMDC could enable phenomena such as topological edge states [20] or the spin Hall effect [21][22][23].To this end, a variety of recent experiments have explored spin transport in graphene/TMDC heterostructures [21,[24][25][26][27][28][29]. Magnetotransport measurements revealed that graphene in contact with WS 2 exhibits a large weak antilocalization (WAL) peak, revealing a strong SOC induced by proximity effects [24][25][26]30]. Fits to the magnetoconductance yielded spin lifetimes τ s ≈ 5 ps, which is two to three orders of magnitude lower than graphene on traditional substrates [10,31]. It was later asserted that after the removal of a temperatureindependent background, τ s becomes at most only a few hundred femtoseconds [26]. Nonlocal Hanle measurements, meanwhile, have revealed spin lifetimes up to a few tens of picoseconds [27][28][29] that can be tuned by a back gate [28,29]. Finally, charge transport measure-

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Giant Spin Lifetime Anisotropy in Graphene Induced by Proximity Effects

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“…For Gr-transition metal dichalcogenide (TMD) heterostructures, an enhanced intrinsic spinorbit coupling (SOC) in the order of 5-15 meV can be induced in graphene, along with a meV order valley-Zeeman splitting due to inequivalent K and K' valleys in graphene [6,9], a Rashba SOC due to breaking of the inversion symmetry at the graphene-TMD interface [3,4] with a possibility of spin-valley coupling [10,11]. This unique ability of the graphene-TMD interface makes it an attractive platform for studying the spin-related proximity induced effects in graphene.…”

Section: Recent Exploration Of Various Two-dimensional (2d) Materialsmentioning

confidence: 99%

“…has provided access to novel charge [1,2] and spin-related phenomena [3][4][5][6][7][8] which are either missing or do not have a measurable effect in intrinsic graphene. Graphene (Gr) can interact with the neighboring material via weak van der Waals interactions which help to preserve its intrinsic charge transport properties while it can still acquire some foreign properties from the host substrate such as a sizable band gap in Gr-on-hexagonal Boron Nitride (hBN) substrate at the Dirac point due to a sublattice dependent crystal potential in graphene [1,2].…”

Section: Recent Exploration Of Various Two-dimensional (2d) Materialsmentioning

confidence: 99%

Spin transport in high-mobility graphene on WS2 substrate with electric-field tunable proximity spin-orbit interaction

Omar

Wees

2018

Phys. Rev. B

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Graphene supported on a transition metal dichalcogenide substrate offers a novel platform to study the spin transport in graphene in presence of a substrate induced spin-orbit coupling, while preserving its intrinsic charge transport properties. We report the first non-local spin transport measurements in graphene completely supported on a 3.5 nm thick tungsten disulfide (WS 2 ) substrate, and encapsulated from the top with a 8 nm thick hexagonal boron nitride layer. For graphene, having mobility up to 16,000 cm 2 V −1 s −1 , we measure almost constant spin-signals both in electron and hole-doped regimes, independent of the conducting state of the underlying WS 2 substrate, which rules out the role of spin-absorption by WS 2 . The spin-relaxation time τ s for the electrons in graphene-on-WS 2 is drastically reduced down to ∼ 10 ps than τ s ∼ 800 ps in graphene-on-SiO 2 on the same chip. The strong suppression of τ s along with a detectable weak anti-localization signature in the quantum magneto-resistance measurements is a clear effect of the WS 2 induced spin-orbit coupling (SOC) in graphene. Via the top-gate voltage application in the encapsulated region, we modulate the electric field by 1 V/nm, changing τ s almost by a factor of four which suggests the electric-field control of the in-plane Rashba SOC. Further, via carrierdensity dependence of τ s we also identify the fingerprints of the D'yakonov-Perel' type mechanism in the hole-doped regime at the graphene-WS 2 interface.

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Van Der Waals Heterostructures with Spin‐Orbit Coupling

Rossi

Triola

2019

Annalen der Physik

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Herein, recent work on van der Waals (vdW) systems in which at least one of the components has strong spin‐orbit coupling is reviewed, focussing on a selection of vdW heterostructures to exemplify the type of interesting electronic properties that can arise in these systems. First a general effective model to describe the low energy electronic degrees of freedom in these systems is presented. The model is then applied to study the case of (vdW) systems formed by a graphene sheet and a topological insulator. The electronic transport properties of such systems are discussed and it is shown how they exhibit much stronger spin‐dependent transport effects than isolated topological insulators. Then, vdW systems are considered in which the layer with strong spin‐orbit coupling is a monolayer transition metal dichalcogenide (TMD) and graphene‐TMD systems are briefly discussed. In the second part of the article, a case is discussed in which the vdW system includes a superconducting layer in addition to the layer with strong spin‐orbit coupling. It is shown in detail how these systems can be designed to realize odd‐frequency superconducting pair correlations. Finally, twisted graphene‐NbSe2 bilayer systems are discussed as an example in which the strength of the proximity‐induced superconducting pairing in the normal layer, and its Ising character, can be tuned via the relative twist angle between the two layers forming the heterostructure.

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Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures

Cited by 116 publications

References 38 publications

Giant Spin Lifetime Anisotropy in Graphene Induced by Proximity Effects

Giant Spin Lifetime Anisotropy in Graphene Induced by Proximity Effects

Spin transport in high-mobility graphene on WS2 substrate with electric-field tunable proximity spin-orbit interaction

Van Der Waals Heterostructures with Spin‐Orbit Coupling

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