Valley magnetoelectricity in single-layer MoS2

Lee, Jieun; Wang, Zefang; Xie, Hongchao; Mak, Kin Fai; Shan, Jie

doi:10.1038/nmat4931

Cited by 175 publications

(202 citation statements)

References 33 publications

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“…9a). This, together with a similar dependence on sample temperature This is reminiscent of the observed σ T in NbSe 2 /Py devices [14], in which we presumed a uniaxial strain induced by the fabrication procedure reduced the nominally high symmetry NbSe 2 structure in such a way that this torque could be generated [36]. Note that for (presumably) strained NbSe 2 /Py devices we observed a large value of τ T , but no τ B .…”

Section: Appendix F: In-plane Field-like Torquesupporting

confidence: 80%

Layer-dependent spin-orbit torques generated by the centrosymmetric transition metal dichalcogenide β−MoTe2

Stiehl

Gupta

et al. 2019

Phys. Rev. B

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Single-crystal materials with sufficiently low crystal symmetry and strong spin-orbit interactions can be used to generate novel forms of spin-orbit torques on adjacent ferromagnets, such as the out-of-plane antidamping torque previously observed in WTe 2 /ferromagnet heterostructures.Here, we present measurements of spin-orbit torques produced by the low-symmetry material β-MoTe 2 , which unlike WTe 2 retains bulk inversion symmetry. We measure spin-orbit torques on β-MoTe 2 /Permalloy heterostructures using spin-torque ferromagnetic resonance as a function of crystallographic alignment and MoTe 2 thickness down to the monolayer limit. We observe an outof-plane antidamping torque with a spin torque conductivity as strong as 1/3 of that of WTe 2 , demonstrating that the breaking of bulk inversion symmetry in the spin-generation material is not a necessary requirement for producing an out-of-plane antidamping torque. We also measure an unexpected dependence on the thickness of the β-MoTe 2 -the out-of-plane antidamping torque is present in MoTe 2 /Permalloy heterostructures when the β-MoTe 2 is a monolayer or trilayer thick, but goes to zero for devices with bilayer β-MoTe 2 .1 arXiv:1906.01068v1 [cond-mat.mes-hall] 3 Jun 2019Spin-orbit torques represent one of the most promising methods for manipulating emerging magnetic memory technologies [1]. When a charge current is applied to a material with large spin-orbit coupling, such as a heavy metal [2][3][4][5][6][7], topological insulator [8,9], or transition metal dichalcogenide (TMD) [10-16], a spin current generated through mechanisms such as the spin Hall or Rashba-Edelstein effects can be used to exert a torque on an adjacent ferromagnet. Recent work from several research groups has focused on understanding how a controlled breaking of symmetry in a spin-generating material / ferromagnet heterostructure can be used to tune the direction of the observed spin-orbit torques for optimal switching of magnetic devices [12][13][14][17][18][19][20][21][22][23][24]. For instance, the presence of magnetic order within a spin-generation layer can allow current-generated spin directions that are typically forbidden for highly-symmetric non-magnetic metals [17][18][19][20]. Similarly, our group has shown that by using WTe 2 as the spin-source material, a TMD with a low-symmetry crystal structure, it is possible to generate an out-of-plane antidamping torque [12,13] -the component of torque required for the most efficient mode of switching for magnets with perpendicular magnetic anisotropy, but forbidden in higher-symmetry materials. Only one other material, SrRuO 3 , has been shown to generate an out-of-plane antidamping spin-orbit torque [20], arising from symmetry breaking associated with magnetic order. Many questions remain regarding the mechanism and necessary conditions for generating a strong out-of-plane antidamping torque.In this work, we study the spin-orbit torques generated in TMD/ferromagnet heterostructures with a crystal symmetry that is distinct from WTe 2 i...

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Section: Appendix F: In-plane Field-like Torquesupporting

confidence: 80%

Layer-dependent spin-orbit torques generated by the centrosymmetric transition metal dichalcogenide β−MoTe2

Stiehl

Gupta

et al. 2019

Phys. Rev. B

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“…Despite the large Ω spin , the Berry curvature dipole remains zero in unstrained MoSSe due to the threefold(C 3 ) symmetry [5]. Physically, the Berry curvature dipole measures the gain in total Berry curvature flux in the current-carrying state [6]. When C 3 -symmetry is present, the Berry flux from left-movers is always equal to that from right-movers on the Fermi surface (middle panel of Fig.1(a)).…”

Section: A Effective Model Hamiltonian Of Strained Mossementioning

confidence: 99%

“…To break the C 3 -symmetry, one feasible way is to introduce uniaxial strains [5,6,11]. Following the scheme developed in the recent work [36], effects of strains in 2D TMDs can be modelled by classifying the strain-field tensor ← → u ij = (∂ i u j + ∂ j u i )/2, (i, j = x, y) according to the irreducible representations of the C 3v point group of polar TMDs.…”

Section: A Effective Model Hamiltonian Of Strained Mossementioning

confidence: 99%

Highly Tunable Nonlinear Hall Effects Induced by Spin-Orbit Couplings in Strained Polar Transition-Metal Dichalcogenides

2020

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Recently, signatures of nonlinear Hall effects induced by Berry curvature dipoles have been found in atomically thin 1T'/T d -WTe2. In this work, we show that in strained polar transition-metal dichalcogenides(TMDs) with 2H-structures, Berry curvature dipoles created by spin degrees of freedom lead to strong nonlinear Hall effects. Under easily accessible uniaxial strain of order ∼ 0.2%, strong nonlinear Hall signals, characterized by Berry curvature dipole in the order of ∼ 1Å, arise in electron-doped polar TMDs such as MoSSe, which is easily detectable experimentally. Moreover, the magnitude and sign of the nonlinear Hall current can be easily tuned by electric gating and strain. These properties can be used to distinguish nonlinear Hall effects from classical mechanisms such as ratchet effects. Importantly, our system provides a potential scheme for building electrically switchable energy harvesting rectifiers.

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“…[77,78] The generation of valley magnetization in electrically biased SL-MoS 2 by a uniaxial strain was also reported recently. [79] Since the strain-induced broken threefold symmetry shifts the valley magnetic moment at ±K points in momentum and the TRS dictates such shifts to be opposite in directions, the resultant Fermi pockets enclose different amounts of magnetic moment at the ±K valleys in the present of charge current, leading to a net magnetization. [80]…”

Section: Valley Magnetizationmentioning

confidence: 99%

Recent Advances in Quantum Effects of 2D Materials

Chen

et al. 2019

Adv Quantum Tech

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The celebrated discovery of graphene has spurred tremendous research interest in two‐dimensional layered materials (2DLMs) with unique attributes in the quantum regime. In 2DLMs, each layer is composed of a covalently bonded lattice and is weakly coupled to its neighboring layers by van der Waals interactions. There are abundant members in this 2DLM family beyond graphene, such as transition metal dichalcogenides (MX2, M = Mo, W; X = S, Se, Te), semimetal chalcogenide (InSe), black phosphorus, etc. The 2DLMs afford rich and ideal material platforms for studying quantum effects and their corresponding applications in the two‐dimensional (2D) limit. In this review, the emerging quantum effects in 2DLMs are examined with particular focus on their band structure evolvement, valleytronics, and quantum Hall/quantum spin Hall effects. Based on the summary of quantum effects discovered in 2DLMs, the future research directions and prospective applications are also discussed.

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Valley magnetoelectricity in single-layer MoS2

Cited by 175 publications

References 33 publications

Layer-dependent spin-orbit torques generated by the centrosymmetric transition metal dichalcogenide β−MoTe2

Layer-dependent spin-orbit torques generated by the centrosymmetric transition metal dichalcogenide β−MoTe2

Highly Tunable Nonlinear Hall Effects Induced by Spin-Orbit Couplings in Strained Polar Transition-Metal Dichalcogenides

Recent Advances in Quantum Effects of 2D Materials

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