Orbital Hall effect in crystals: Interatomic versus intra-atomic contributions

Pezo, Armando; Ovalle, Diego García; Manchon, Aurélien

doi:10.1103/physrevb.106.104414

Cited by 22 publications

(11 citation statements)

References 46 publications

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“…Theoretical calculations have predicted the OHE to be universal due to the ubiquity of orbital textures in several transition metals with weak SOC 42 . However, important questions as to the exact role of intra-and interatomic contributions need to be answered in order to extend models to more complex systems 43 . Relevant orbital texture in BPBO originates from the strong spσ interactions and nearest neighbor hopping.…”

Section: Discussionmentioning

confidence: 99%

Giant room-temperature spin-orbit torque in a bismuthate superconductor

Edgeton

Harris

Campbell

et al. 2023

Preprint

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The emergence of artificial intelligence and machine-learning-based systems, in conjunction with the pervasive implementation of the internet of things has put a strong emphasis on the energy efficiency of computing. This has triggered research on multiple pathways to improve computing efficiency, spanning 3-D integration of logic and memory as well as new, physics-based pathways including those embracing the electron’s spin degree of freedom, namely spintronics. Concurrently, the proposed integration of superconductivity and spintronics emphasizes complex oxides as a promising platform which in principle can integrate spin current manipulation and high temperature superconductivity within the same complex system. Here, we report giant spin-orbit torque (SOT) discovered in the normal state of a complex oxide superconductor, Ba(Pb,Bi)O3, which provides isotropic and easily manipulated superconducting properties. Using spin-torque ferromagnetic resonance (ST-FMR) and d.c. non-linear Hall measurements, we find a robust SOT efficiency exceeding unity and demonstrate current driven magnetization switching at current densities as low as \(4\times {10}^{5}\text{A}{\text{c}\text{m}}^{-2}\). The hybridized s-p orbital character at the Fermi energy makes this an unexpectedly large value. We postulate the presence of an unconventional SOT generation in bismuthate heterostructures and anticipate our results will trigger further exploration of such complex oxides for the development of superconducting spintronics.

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Section: Discussionmentioning

confidence: 99%

Giant room-temperature spin-orbit torque in a bismuthate superconductor

Edgeton

Harris

Campbell

et al. 2023

Preprint

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“…Analogous to the generalized Berry curvature, 24,25,56,60 we write the orbital Berry curvature which characterizes the magnon orbital Nernst transport as follows:…”

Section: Model Constructionmentioning

confidence: 99%

“…In electronics systems, on the other hand, there have been studies showing that electrons can exhibit a Hall effect without spin–orbit coupling, owing to their orbital degree of freedom. − This discovery evoked a surge of interest in electron–orbital transport phenomena such as the orbital Hall effect − and the orbital torque. − Moreover, there have been theoretical suggestions that orbital-dependent electron transport critically affects electron spin dynamics when spin–orbit coupling is present. For instance, it has been suggested − that the orbital Hall effect may play a crucial role in the spin Hall effect.…”

mentioning

confidence: 99%

“…We define the magnon orbital moment operator as L̂ = 1/4( r × v – v × r ) analogously to the electron orbital moment in the modern theory for orbital magnetization. − Note that this orbital moment differs from the orbital angular momentum by dimension of mass. Analogous to the well-known formula of the intrinsic orbital moment in electron systems, we read the expectation value of the magnon orbital moment ,,,− , ⟨ n false| boldL̂ false| n ⟩ = ⟨ n true| ( r × v − v × r 4 ) true| n ⟩ infix= prefix− i 2 ℏ false⟨ ∂ boldk n | × false( scriptH boldk − σ 3 ϵ̅ n , boldk false) | ∂ boldk n false⟩ which can be interpreted as the manifestation of the self-rotation of a wave packet within the wave packet formalism . The magnon orbital moment profiles L z n ( k ) = ⟨ n false| L̂ z false| n ⟩ of the two magnons are shown in Figure e and ...…”

mentioning

confidence: 99%

“…However, our system can exhibit the intrinsic Nernst effect of the magnon orbital moment because both L z n ( k ) and Ω z n ( k ) are odd in k , and thus their product L z n ( k ) Ω z n ( k ) is k -even. Analogous to the generalized Berry curvature, ,,, we write the orbital Berry curvature which characterizes the magnon orbital Nernst transport as follows: normalΩ n L ( k ) = prefix− prefix∑ m ≠ n false( σ 3 false) m m false( σ 3 false) n n 2 normalℏ 2 Im [ false⟨ n | j z , y L | m false⟩ false⟨ m | v x | n false⟩ ] false( ϵ̅ n , boldk − ϵ̅ m , boldk false) 2 where j z , y L = ( υ y σ 3 L̂ z + L̂ z <...…”

mentioning

confidence: 99%

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Magnon Orbital Nernst Effect in Honeycomb Antiferromagnets without Spin–Orbit Coupling

Go,

An,

Lee

et al. 2024

Nano Lett.

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Recently, topological responses of magnons have emerged as a central theme in magnetism and spintronics. However, resulting Hall responses are typically weak and infrequent, since, according to present understanding, they arise from effective spin−orbit couplings, which are weaker compared to the exchange energy. Here, by investigating transport properties of magnon orbital moments, we predict that the magnon orbital Nernst effect is an intrinsic characteristic of the honeycomb antiferromagnet and therefore, it manifests even in the absence of spin−orbit coupling. For the electric detection, we propose an experimental scheme based on the magnetoelectric effect. Our results break the conventional wisdom that the Hall transport of magnons requires spin−orbit coupling by predicting the magnon orbital Nernst effect in a system without it, which leads us to envision that our work initiates the intensive search for various magnon Hall effects in generic magnetic systems with no reliance on spin−orbit coupling.

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Spintronics meets orbitronics: Emergence of orbital angular momentum in solids

Jo,

Go,

Choi

et al. 2024

npj Spintronics

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One of the ultimate goals of spintronics is to realize an efficient electrical manipulation of spin for high-speed and low-power nanodevices. A core ingredient for achieving this goal is the relativistic interaction between the electron’s orbital motion and spin, but the properties of the orbital angular momentum itself have remained largely unexplored. However, recent theories and experiments have uncovered that electrons may acquire nonvanishing orbital angular momentum when an external electric field is applied, even without the spin–orbit coupling. These findings have spurred the emergence of a burgeoning field known as orbitronics, which harnesses the orbital angular momentum to manipulate magnetic devices. In this Review, we provide an overview of the recent developments in orbitronics and discuss their implications for spintronics. We then outline future avenues of research at the intersection of spintronics and orbitronics.

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Orbital Hall effect in crystals: Interatomic versus intra-atomic contributions

Cited by 22 publications

References 46 publications

Giant room-temperature spin-orbit torque in a bismuthate superconductor

Giant room-temperature spin-orbit torque in a bismuthate superconductor

Magnon Orbital Nernst Effect in Honeycomb Antiferromagnets without Spin–Orbit Coupling

Spintronics meets orbitronics: Emergence of orbital angular momentum in solids

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