Unveiling the mechanisms of the spin Hall effect in Ta

Sagasta, Edurne; Omori, Yasutomo; Vélez, Saül; Llopis, Roger; Tollan, Christopher; Chuvilin, Andrey; Hueso, Luis E.; Gradhand, Martin; Otani, Y.; Casanova, Fèlix

doi:10.1103/physrevb.98.060410

Cited by 68 publications

(74 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the one hand, we find that, for 2 values similar or longer than the thickness of MoTe2 (11 nm), | | tends to a low constant value independent of 2 , because the SCC process is limited by the MoTe2 thickness. This behavior allows us to get a lower limit for | |, which for the case of the conventional component is | | ≥ 0.21 at room temperature, comparable to the best known spin Hall metals 24,25 and alloys 23,44 . The lower limit for the unconventional component efficiency is also found to be remarkably large (| | ≥ 0.10), and with opposite sign, at room temperature.…”

mentioning

confidence: 73%

“…On the other hand, for 2 values much smaller than the MoTe2 thickness, it is the | | 2 product that tends to a low constant value, which is what defines the SCC efficiency 45,46 . This allows us to give a lower limit for | | 2 , which for the case of the conventional component is | | 2 ≥ 1.15 nm at room temperature, much larger than heavy metals (~0.1−0.3 nm) 24,25 . If we assume that the SCC originates at the surface states of MoTe2, this product would correspond to the Edelstein length ( ), the efficiency associated to the inverse Edelstein effect.…”

mentioning

confidence: 99%

“…These trends can be explained when an additional mechanism contributes to the SCC. One possibility is an extrinsic (skew scattering and/or side jump) contribution to the SHE with opposite sign 25,48 . Another possibility is the presence of the inverse Edelstein effect in graphene induced by spin-orbit proximity with MoTe2, which would be detected with the same measurement configuration and has been recently reported in other graphene/TMDs van der Waals heterostructures 40,[49][50][51] .…”

mentioning

confidence: 99%

See 2 more Smart Citations

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe₂ at Room Temperature

et al. 2019

Self Cite

View full text Add to dashboard Cite

Efficient and versatile spin-to-charge current conversion is crucial for the development of spintronic applications, which strongly rely on the ability to electrically generate and detect spin currents. In this context, the spin Hall effect has been widely studied in heavy metals with strong spinorbit coupling. While the high crystal symmetry in these materials limits the conversion to the orthogonal configuration, unusual configurations are expected in low symmetry transition metal dichalcogenide semimetals, which could add flexibility to the electrical injection and detection of pure spin currents. Here, we report the observation of spin-to-charge conversion in MoTe2 flakes, which are stacked in graphene lateral spin valves. We detect two distinct contributions arising from the conversion of two different spin orientations. In addition to the conventional conversion where the spin polarization is orthogonal to the charge current, we also detect a conversion where the spin polarization and the charge current are parallel. Both contributions, which could arise either from bulk spin Hall effect or surface Edelstein effect, show large efficiencies comparable to the best spin Hall metals and topological insulators. Our finding enables the simultaneous conversion of spin currents with any in-plane spin polarization in one single experimental configuration.Symmetry is a unifying principle that governs all aspects of Physics, from the model of atomic orbitals to the Landau theory of phase transitions. The physical properties of crystalline solids are also highly constrained by symmetry 1 and, in turn, as symmetry is progressively lowered through the 32 crystallographic point groups, novel transport effects emerge, such as the non-linear Hall effect 2 , the spin galvanic effect 3 and the valley magnetoelectricity 4 in non-centrosymmetric crystals, and the magnetochiral anisotropy 5 in chiral crystals. Crystal symmetry dictates also the geometry of a phenomenon that has attracted a lot of attention in recent years, the spin Hall effect (SHE) or its reciprocal effect [inverse SHE (ISHE)], which are generally observed in materials possessing strong spin-orbit coupling (SOC), and enables the interconversion between charge and spin currents. In conventional spin Hall materials, high crystal symmetry imposes that injecting a charge current density ( ) can only result in a transverse spin current density ( ) with a spin polarization ( ) orthogonal to both and (Figure 1a) 6 . SHE/ISHE are crucial effects for the electrical generation or detection of spin current, required in applications such as spin-orbit torque memories 7,8,9 and spin-based logic devices 10,11 . These applications would highly benefit from more versatile SHE/ISHE configurations which can be obtained by lifting the constraints imposed by high crystal symmetry and enabling unusual spin-to-charge conversion geometries in low-symmetry crystals 12,13,14 (Figures 1b,c).

show abstract

mentioning

confidence: 73%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe₂ at Room Temperature

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Spin Hall materials are usually found either among elemental metals with strong SOC [35][36][37] or novel topological phases, such as Weyl and Dirac nodal line semimetals where spin-orbit protected gaps between the electronic bands are crossed by the Fermi level. [38][39][40] It has also been known that a giant Rashba effect (RE) could induce large SHC as long as the Fermi level can be tuned and brought between lower and upper Rashba bands.…”

Section: Electronic Properties and Spin Hall Effectmentioning

confidence: 99%

Spin Hall effect in prototype Rashba ferroelectrics GeTe and SnTe

et al. 2020

View full text Add to dashboard Cite

Ferroelectric Rashba semiconductors (FERSC) have recently emerged as a promising class of spintronics materials. The peculiar coupling between spin and polar degrees of freedom responsible for several exceptional properties, including ferroelectric switching of Rashba spin texture, suggests that the electron's spin could be controlled by using only electric fields. In this regard, recent experimental studies revealing charge-to-spin interconversion phenomena in two prototypical FERSC, GeTe and SnTe, appear extremely relevant. Here, by employing density functional theory calculations, we investigate spin Hall effect (SHE) in these materials and show that it can be large either in ferroelectric or paraelectric structure. We further explore the compatibility between doping required for the practical realization of SHE in semiconductors and polar distortions which determine Rashbarelated phenomena in FERSC, but which could be suppressed by free charge carriers. Based on the analysis of the lone pairs which drive ferroelectricity in these materials, we have found that the polar displacements in GeTe can be sustained up to a critical hole concentration of over ∼ 10 21 /cm 3 , while the tiny distortions in SnTe vanish at a minimal level of doping. Finally, we have estimated spin Hall angles for doped structures and demonstrated that the spin Hall effect could be indeed achieved in a polar phase. We believe that the confirmation of spin Hall effect, Rashba spin textures and ferroelectricity coexisting in one material will be helpful for design of novel multifunctional spintronics devices operating without magnetic fields.

show abstract

“…We further characterize the spin Hall conductivity of W by analyzing the relation between

| ξ_{DL} |

and the measured W layers' resistivity

false(ρ_{W} false)

. The spin Hall conductivity

| σ_{SH} | = false| ξ_{DL} false| / ρ_{W}

can be extracted from the linear slope of

| ξ_{DL} |

versus

ρ_{normalW}

plot, if the observed SHE is intrinsic in nature . Interestingly, there exists two linear regimes, which correspond to

| σ_{SH}^{α‐W} | \approx 3.71 \times 10^{5} {normalΩ}^{- 1} {normalm}^{- 1}

for α‐W‐dominated samples and

| σ_{SH}^{amorphous‐W} | \approx 1.05 \times 10^{5} {normalΩ}^{- 1} {normalm}^{- 1}

for amorphous‐W‐dominated samples (Figure b).…”

mentioning

confidence: 99%

Current‐Induced Magnetization Switching by the High Spin Hall Conductivity α‐W

Liao

Chen

Ferrante

et al. 2019

Physica Rapid Research Ltrs

View full text Add to dashboard Cite

The spin Hall effect originating from 5d heavy transition‐metal thin films such as Pt, Ta, and W is able to generate efficient spin–orbit torques that can switch adjacent magnetic layers. This mechanism can serve as an alternative to conventional spin‐transfer torque for controlling next‐generation magnetic memories. Among all 5d transition metals, W in its resistive amorphous phase typically shows the largest spin–orbit torque efficiency ≈0.20–0.50. In contrast, its conductive and crystalline α phase possesses a significantly smaller efficiency of ≈0.03 and no spin–orbit torque switching is realized using α‐W thin films as the spin Hall source. Herein, through a comprehensive study of high‐quality W/CoFeB/MgO and the reversed MgO/CoFeB/W magnetic heterostructures, it is shown that although amorphous‐W has a greater spin–orbit torque efficiency, the spin Hall conductivity of α‐W (|σSHα‐W|=3.71×105 normalΩ−1 normalm−1) is ≈3.5 times larger than that of amorphous W (|σSHamorphous‐W|=1.05×105 normalΩ−1 normalm−1). Moreover, spin–orbit torque‐driven magnetization switching using a MgO/CoFeB/α‐W heterostructure is demonstrated. The findings suggest that the conductive and high spin Hall conductivity α‐W is a potential candidate for future low‐power consumption spin–orbit torque memory applications.

show abstract

Unveiling the mechanisms of the spin Hall effect in Ta

Cited by 68 publications

References 56 publications

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe₂ at Room Temperature

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe₂ at Room Temperature

Spin Hall effect in prototype Rashba ferroelectrics GeTe and SnTe

Current‐Induced Magnetization Switching by the High Spin Hall Conductivity α‐W

Contact Info

Product

Resources

About

Unveiling the mechanisms of the spin Hall effect in Ta

Cited by 68 publications

References 56 publications

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe2 at Room Temperature

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe2 at Room Temperature

Spin Hall effect in prototype Rashba ferroelectrics GeTe and SnTe

Current‐Induced Magnetization Switching by the High Spin Hall Conductivity α‐W

Contact Info

Product

Resources

About

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe₂ at Room Temperature

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe₂ at Room Temperature