Controlling spin current polarization through non-collinear antiferromagnetism

Abstract The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn3GaN, in which the triangular spin structure creates a low magnetic symmetry while maintaining a high crystalline symmetry. We demonstrate that epitaxial Mn3GaN/permalloy heterostructures can generate unconventional spin-orbit torques at room temperature corresponding to out-of-plane and Dresselhaus-like spin polarizations which are forbidden in any sample with two-fold rotational symmetry. Our results demonstrate an approach based on spin-structure design for controlling spin-orbit torque, enabling high-efficient antiferromagnetic spintronics.

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Spin currents in semiconductor nanostructures: A non-equilibrium Green-function approach

10.1093/oxfordhb/9780199533046.013.24 ◽

2017 ◽

Author(s):

Branislav K. Nikolic ◽

Liviu P. Zarbo ◽

Satofumi Souma

Keyword(s):

Green Function ◽

Spin Current ◽

Semiconductor Nanostructures ◽

Pure Spin ◽

Current Operator ◽

Spin Orbit ◽

Spin Currents ◽

Low Dimensional ◽

Green Function Approach ◽

Non Equilibrium

This article examines spin currents and spin densities in realistic open semiconductor nanostructures using different tools of quantum-transport theory based on the non-equilibrium Green function (NEGF) approach. It begins with an introduction to the essential theoretical formalism and practical computational techniques before explaining what pure spin current is and how pure spin currents can be generated and detected. It then considers the spin-Hall effect (SHE), and especially the mesoscopic SHE, along with spin-orbit couplings in low-dimensional semiconductors. It also describes spin-current operator, spindensity, and spin accumulation in the presence of intrinsic spin-orbit couplings, as well as the NEGF approach to spin transport in multiterminal spin-orbit-coupled nanostructures. The article concludes by reviewing formal developments with examples drawn from the field of the mesoscopic SHE in low-dimensional spin-orbit-coupled semiconductor nanostructures.

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Different types of spin currents in the comprehensive materials database of nonmagnetic spin Hall effect

npj Computational Materials ◽

10.1038/s41524-021-00635-0 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Yang Zhang ◽

Qiunan Xu ◽

Klaus Koepernik ◽

Roman Rezaev ◽

Oleg Janson ◽

...

Keyword(s):

Hall Effect ◽

Mirror Symmetry ◽

Spin Current ◽

Strong Relationship ◽

Nodal Line ◽

Spin Hall Effect ◽

Spin Currents ◽

Different Types ◽

Symmetry Protected ◽

Crystalline Symmetry

AbstractSpin Hall effect (SHE) has its special position in spintronics. To gain new insight into SHE and to identify materials with substantial spin Hall conductivity (SHC), we performed high-precision high-throughput ab initio calculations of the intrinsic SHC for over 20,000 nonmagnetic crystals. The calculations revealed a strong relationship between the magnitude of the SHC and the crystalline symmetry, where a large SHC is typically associated with mirror symmetry-protected nodal line band structures. This database includes 11 materials with an SHC comparable to or even larger than that of Pt. Materials with different types of spin currents were additionally identified. Furthermore, we found that different types of spin current can be obtained by rotating applied electrical fields. This improves our understanding and is expected to facilitate the design of new types of spin-orbitronic devices.

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Magnetic crystalline-symmetry-protected axion electrodynamics and field-tunable unpinned Dirac cones in EuIn2As2

Nature Communications ◽

10.1038/s41467-021-21154-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

S. X. M. Riberolles ◽

T. V. Trevisan ◽

B. Kuthanazhi ◽

T. W. Heitmann ◽

F. Ye ◽

...

Keyword(s):

Density Functional ◽

Surface States ◽

Antiferromagnetic Order ◽

Functional Theory ◽

Magnetic Symmetry ◽

Integer Quantum ◽

Symmetry Protected ◽

Topological Crystalline Insulator ◽

Low Symmetry ◽

Crystalline Symmetry

AbstractKnowledge of magnetic symmetry is vital for exploiting nontrivial surface states of magnetic topological materials. EuIn2As2 is an excellent example, as it is predicted to have collinear antiferromagnetic order where the magnetic moment direction determines either a topological-crystalline-insulator phase supporting axion electrodynamics or a higher-order-topological-insulator phase with chiral hinge states. Here, we use neutron diffraction, symmetry analysis, and density functional theory results to demonstrate that EuIn2As2 actually exhibits low-symmetry helical antiferromagnetic order which makes it a stoichiometric magnetic topological-crystalline axion insulator protected by the combination of a 180∘ rotation and time-reversal symmetries: $${C}_{2}\times {\mathcal{T}}={2}^{\prime}$$ C 2 × T = 2 ′ . Surfaces protected by $${2}^{\prime}$$ 2 ′ are expected to have an exotic gapless Dirac cone which is unpinned to specific crystal momenta. All other surfaces have gapped Dirac cones and exhibit half-integer quantum anomalous Hall conductivity. We predict that the direction of a modest applied magnetic field of μ0H ≈ 1 to 2 T can tune between gapless and gapped surface states.

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Observation of the Out‐of‐Plane Polarized Spin Current from CVD Grown WTe 2

Advanced Quantum Technologies ◽

10.1002/qute.202100038 ◽

2021 ◽

pp. 2100038

Author(s):

Shuyuan Shi ◽

Jie Li ◽

Chuang‐Han Hsu ◽

Kyusup Lee ◽

Yi Wang ◽

...

Keyword(s):

Spin Current ◽

Out Of Plane

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Anomalous spin Hall and inverse spin Hall effects in magnetic systems

Communications Physics ◽

10.1038/s42005-021-00557-9 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

X. R. Wang

Keyword(s):

Hall Effect ◽

Order Parameter ◽

Spin Current ◽

Spin Hall Effect ◽

Magnetic Systems ◽

Charge Current ◽

Spin Currents ◽

Tensor Quantity ◽

Hall Effects ◽

Spin Hall Effects

AbstractSpin current is a very important tensor quantity in spintronics. However, the well-known spin-Hall effect (SHE) can only generate a few of its components whose propagating and polarization directions are perpendicular with each other and to an applied charge current. It is highly desirable in applications to generate spin currents whose polarization can be in any possible direction. Here anomalous SHE and inverse spin-Hall effect (ISHE) in magnetic systems are predicted. Spin currents, whose polarisation and propagation are collinear or orthogonal with each other and along or perpendicular to the charge current, can be generated, depending on whether the applied charge current is along or perpendicular to the order parameter. In anomalous ISHEs, charge currents proportional to the order parameter can be along or perpendicular to the propagating or polarization directions of the spin current.

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Layer- and gate-tunable spin-orbit coupling in a high-mobility few-layer semiconductor

Science Advances ◽

10.1126/sciadv.abe2892 ◽

2021 ◽

Vol 7 (5) ◽

pp. eabe2892

Author(s):

Dmitry Shcherbakov ◽

Petr Stepanov ◽

Shahriar Memaran ◽

Yaxian Wang ◽

Yan Xin ◽

...

Keyword(s):

Electric Field ◽

High Mobility ◽

Orbit Coupling ◽

Spin Splitting ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Quantum Oscillations ◽

Out Of Plane ◽

Order Of Magnitude ◽

Spin Degeneracy

Spin-orbit coupling (SOC) is a relativistic effect, where an electron moving in an electric field experiences an effective magnetic field in its rest frame. In crystals without inversion symmetry, it lifts the spin degeneracy and leads to many magnetic, spintronic, and topological phenomena and applications. In bulk materials, SOC strength is a constant. Here, we demonstrate SOC and intrinsic spin splitting in atomically thin InSe, which can be modified over a broad range. From quantum oscillations, we establish that the SOC parameter α is thickness dependent; it can be continuously modulated by an out-of-plane electric field, achieving intrinsic spin splitting tunable between 0 and 20 meV. Unexpectedly, α could be enhanced by an order of magnitude in some devices, suggesting that SOC can be further manipulated. Our work highlights the extraordinary tunability of SOC in 2D materials, which can be harnessed for in operando spintronic and topological devices and applications.

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