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The asymmetric photonic spin Hall effect (APSHE) induced by surface plasmon polaritons in a graphene-based structure is actively manipulated by external magnetic field and electric field. It is revealed that the spin-dependent splitting exhibits spatio-temporal asymmetric property due to the involvement of the anisotropic graphene. The peak of asymmetry degree in APSHE at the position of reflectance valley corresponds toward a smaller incident angle with the increase of magnetic field intensity or Fermi energy, which is attributed to the tunability of reflectance for the graphene-based structure. Based on the asymmetric splitting shift, a potential application is proposed for detecting low concentration gas molecules and the detection resolution can be dynamically tunable by changing the magnetic field intensity and Fermi energy. This study may provide a new reference in the fabrication of graphene-based plasmonic sensor devices. [ABSTRACT FROM AUTHOR]

We demonstrate that a magnetic tunnel junction injected with a spin Hall current can exhibit linear rotation of the magnetization of the free-ferromagnet using only the spin current. Using the linear resistance change of the magnetic tunnel junction (MTJ), we devise a circuit for the rectified linear activation (ReLU) function of the artificial neuron. We explore the role of different spin Hall effect (SHE) heavy metal (HM) layers on the power consumption of the ReLU circuit. We benchmark the power consumption of the ReLU circuit with different SHE layers by defining a new parameter called the spin Hall power factor. It combines the spin Hall angle, resistivity, and thickness of the HM layer, which translates to the power consumption of the different SHE layers during spin-orbit switching/rotation of the free FM. We employ a hybrid spintronics-CMOS simulation framework that couples Keldysh non-equilibrium Green's function formalism with Landau–Lifshitz–Gilbert–Slonzewski equations and the HSPICE circuit simulator to account for the diverse physics of spin-transport and the CMOS elements in our proposed ReLU design. We also demonstrate the robustness of the proposed ReLU circuit against thermal noise and a non-trivial power-error trade-off that enables the use of an unstable free-ferromagnet for energy-efficient design. Using the proposed circuit, we evaluate the performance of the convolutional neural network for MNIST datasets and demonstrate comparable classification accuracies to the ideal ReLU with an energy consumption of 75 pJ per sample. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the photonic spin Hall effect (PSHE) in the combined structure of periodic dielectric waveguides (PDWs) and photonic crystal waveguide (PCW). By controlling the polarization of the dipole source, we have successfully achieved the arbitrary manipulation of PSHE for the PDW guided mode in our structure. The advantage of PDW is that it can be designed to different shapes without the geometric constraints, and still maintains a relatively high transmission rate. Therefore, by further changing the structure, including the adjustment of the intersection angle between PDW and PCW, and the alteration of the straight PDW to the bending or bifurcated shapes, we find that the output of highly unidirectional PSHE is mainly determined by the intersection angle between PDW and PCW and almost independent of the detailed shape of PDW. [ABSTRACT FROM AUTHOR]

We systematically explore the origin and evolution of the exceptional points (EP) when a light beam is scattered by a parity-time (PT)-symmetric system using a scattering matrix approach and a full-wave theory. It is demonstrated that the PT-symmetric system switches between symmetry and symmetry-breaking phases at the EPs, giving rise to singular features in the Fresnel coefficients and causing the spin-Hall effect (SHE) near the EPs to exhibit anomalous features such as significantly enhanced transverse spin-Hall shifts and additional in-plane spin-Hall shifts. This exotic SHE can be explained by the significant beam intensity distortion caused by the destructive interference between the spin-maintained normal modes and the spin-reversed abnormal modes in the scattered light. This phenomenon can further be understood in terms of vortex mode decomposition, wherein it can be interpreted as the competition and superposition of three vortex modes with topological charges of −1, 0, and 1, respectively. These findings elucidate the mechanism of the unusual SHE around the EPs and offer potential avenues for EP-based sensing and structured light manipulation.

With the recent discovery of three dimensional Dirac semimetals, their integrations with the optoelectronic devices allow the novel optical effects and functionalities. Here, we theoretically report the photonic spin Hall effect in a periodic structure, where three dimensional Dirac semimetals and the dielectric materials are assembled into the stack. The incident angle and frequency dependent spin shift spectrum reveals that the spin shifts of the transmitted wave in this structure emerge the obvious peaks and valleys for the horizontal polarized wave and their magnitudes and positions display a distinct dependence on the incident angle around the specific frequency. These observations originate from its zero value of the effective perpendicular permittivity and its greatly reduced transmission in the multilayered structure, whose mechanism is different from those in the previous works. Moreover, both the peaks and valleys of the transmitted spin shift are significantly sensitive to the Fermi energy of three dimensional Dirac semimetals, whose magnitudes and positions can be tuned by varying it. Our results highlight the vital role of three dimensional Dirac semimetals in their applications of the spin photonic devices and pave the way to explore the tunable photonic spin Hall effect by engineering their Fermi energies. [ABSTRACT FROM AUTHOR]

Canted antiferromagnets offer great potential in fundamental research and for use in applications due to their unique properties. The presence of the Dzyaloshinskii–Moriya interaction (DMI) leads to the existence of a weak ferromagnetic moment at room temperature. We study both theoretically and experimentally microwave spin pumping by a quasi-ferromagnetic mode from a canted easy plane antiferromagnet with weak ferromagnetism FeBO3. The conversion of a microwave signal into a constant voltage is realized using the inverse spin Hall effect in an iron borate/heavy metal heterostructure. We use an additional bias magnetic field to selectively tune the resonance frequency of such a microwave detector over a wide range up to 43.5 GHz with a potential sensitivity near 2.5 µ V W−1. We confirm the pure spin current nature by changing the polarity of the detected via inverse spin Hall effect voltage by switching the direction of the bias magnetic field. We believe that our results will be useful for the development of highly tunable, portable and sensitive microwave antiferromagnet-based functional devices. [ABSTRACT FROM AUTHOR]

Quantum anomalous Hall effect (QAHE) and quantum spin Hall effect (QSHE) are two interesting physical manifestations of 2D materials that have an intrinsic nontrivial band topology. In principle, they are ground-state equilibrium properties characterized by Fermi level lying in a topological gap, below which all the occupied bands are summed to a non-zero topological invariant. Here, we propose theoretical concepts and models of ‘excited’ QAHE (EQAHE) and EQSHE generated by dissociation of an excitonic insulator (EI) state with complete population inversion (CPI), a unique many-body ground state enabled by two yin-yang flat bands (FBs) of opposite chirality hosted in a diatomic Kagome lattice. The two FBs have a trivial gap in between, i.e. the system is a trivial insulator in the single-particle ground-state, but nontrivial gaps above and below, so that upon photoexcitation the quasi-Fermi levels of both electrons and holes will lie in a nontrivial gap achieved by the CPI-EI state, as demonstrated by exact diagonalization calculations. Then dissociation of singlet and triplet EI state will lead to EQAHE and EQSHE, respectively. Realizations of yin-yang FBs in real materials are also discussed. [ABSTRACT FROM AUTHOR]

The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of left- and right-handed circularly polarized light, holds great potential for applications in optical sensors, precise metrology and nanophotonic devices. In this paper, we present the significant enhancement of photonic SHE in the terahertz range by considering the InSb-supported long-range surface plasmon resonance (LRSPR) effect. The influences of the InSb/ENZ layer thickness and temperature on the photonic SHE were investigated. With the optimal structural parameters and temperature, the maximal spin shift of the horizontal polarization light can reach up to 2.68 mm. Moreover, the spin shift is very sensitive to the refractive index change of gas, and thus a terahertz gas sensing device with a superior intensity sensitivity of 2.5 Ă— 105 ÎĽm/RIU is proposed. These findings provide an effective method to enhance the photonic SHE in the terahertz range and therefore offer the opportunity for developing the terahertz optical sensors based on photonic SHE. [ABSTRACT FROM AUTHOR]

The effective control of skyrmion motion is a critical aspect for realizing skyrmion-based devices. Among the potential directions, the use of current induced spin–orbit torque (SOT) is energetically efficient. However, the conventional heavy metals with high crystal symmetry limit the charge-to-spin conversion to the orthogonal configuration, which causes the skyrmions to deflect from the electrical current direction with a finite skyrmion Hall angle. Here, we investigate the SOT driven skyrmion motion under unconventional spin Hall effect. We systematically study the effect of a noncollinear low-symmetry spin source layer with spin moments mixed by Rashba-like S _y , Dresselhaus-like S _x and out-of-plane like S _z on skyrmion features (velocity, diameter and Hall angle) stabilized in a ferromagnet/WTe _2 heterostructure. Our results may provide a new degree of freedom for controlling the skyrmion Hall angle, and can open the way for the discovery of new ferromagnetic multilayer where the skyrmion Hall angle is suppressed by the proper design of different SOT driven forces.

High spin to charge conversion efficiency is a requirement for spintronic devices, which are governed by spin pumping and the inverse spin Hall effect (ISHE). In the last decade, ISHE and spin pumping have been heavily investigated in ferromagnet/heavy metal (HM) heterostructures. Recently, antiferromagnetic (AFM) materials have been found to be a good replacement for HMs because AFMs exhibit terahertz spin dynamics, high spin–orbit coupling, and absence of the stray field. In this context, we have performed the ISHE in CoFeB/IrMn heterostructures. Spin pumping studies are carried out for Co40Fe40B20(12 nm)/Cu(3 nm)/Ir50Mn50(t nm)/AlOx(3 nm) samples where t value varies from 0 to 10 nm. Damping in all the samples is higher than in the single layer CoFeB which indicates that spin pumping due to IrMn is the underneath mechanism. Further, the spin pumping in the samples is confirmed by angle dependent ISHE measurements. We have also disentangled other spin rectifications effects and found that the spin pumping is dominant in all the samples. From the ISHE analysis the real part of spin mixing conductance () is found to be 0.704 ± 0.003 × 1018 m−2. [ABSTRACT FROM AUTHOR]

We introduce a generalized Rashba coupling approximation to analytically solve confined two-dimensional electron systems with both the Rashba and Dresselhaus spin–orbit couplings in an external magnetic field. A solvable Hamiltonian is obtained by performing a simple change of basis, which has the same form as that with only Rashba coupling. Each Landau state becomes a new displaced-Fock state instead of the original Harmonic oscillator Fock state. Analytical energies are consistent with the numerical ones in a wide range of coupling strength even for a strong Zeeman splitting, exhibiting the validity of the analytical approximation. By using the eigenstates, spin polarization correctly displays a jump at the energy-level crossing point, where the corresponding spin conductance exhibits a pronounced resonant peak. As the component of the Dresselhaus coupling increases, the resonant point shifts to a smaller value of the magnetic field. In contrast to pure Rashba couplings, we find that the Dresselhaus coupling and Zeeman splittings tend to suppress the resonant spin Hall effect. Our method provides an easy-to-implement analytical treatment to two-dimensional electron gas systems with both types of spin–orbit couplings by applying a magnetic field. [ABSTRACT FROM AUTHOR]

The latest research suggests that strain can be utilized to engineer the electronic states of Weyl semimetals (WSMs) through creating a pseudo-magnetic field B el. The response of strained WSMs to a real time-varying electric field E with E ⊥ B el can cause spatial chirality and charge separation in WSMs, i.e., the chiral Hall effect (CHE). Herein, the photonic spin Hall effect (PSHE) modified by CHE in strained WSM thin films is studied. We show that the in-plane and transverse photonic spin-dependent shifts (⟨Δx+⟩ and ⟨Δy+⟩) can be tuned to be more than 400 and 50 times of incident wavelength, respectively, at the angular frequency being close to the cyclotron frequency of massless fermions in the pseudo-magnetic field. In order to enhance the PSHE, epsilon-near-zero materials take priority of being as the substrates of WSM films. Besides, both ⟨Δx+⟩ and ⟨Δy+⟩ generally give extreme values around incident angles at which Fresnel reflection coefficients exhibit local minimums, whereas an inversion-symmetry breaking with nonzero axial chemical potential may break this generality. Finally, one possible experimental strategy for observing this CHE tuned PSHE is schemed, which may provide a pristine optical technique to precisely engineer and detect the strain in topological materials. [ABSTRACT FROM AUTHOR]

In this paper, by utilizing the transfer matrix method, a structure composed of one-dimensional (1D) periodic multilayer dielectrics, InSb, and nonlinear material is proposed to investigate the behavior of the spin Hall effect of light (SHEL) and its nonreciprocity and bistable features. The results demonstrate that, as the light intensity increases, the reflection coefficients under both TM and TE waves have a bistable phenomenon, and the points of both horizontal and vertical displacements are consistent with the regions where reflection is close to 0. Furthermore, to make our study complete, the thicknesses of the nonlinear and InSb layers are adjusted to study the effects on the performance of SHEL, and it can be found that, with the escalation of the thicknesses of the nonlinear and InSb layers, all the points of displacements are shifting to the direction of the angle. Besides, all parameters demonstrate the phenomenon of nonreciprocity. This research supplies meaningful guidelines for some optical instruments, such as light intensity sensors. [ABSTRACT FROM AUTHOR]

The photonic spin Hall effect (SHE) holds great potential applications in manipulating spin-polarized photons. However, the SHE is generally very weak, and previous studies of amplifying photonic SHE were limited to the incident light in a specific wavelength range. In this paper, we propose a four-layered nanostructure of prism-graphene-air-substrate, and the enhanced photonic SHE of reflected light in broadband range of 0 THz–500 THz is investigated theoretically. The spin shift can be dynamically modulated by adjusting the thickness of air gap, Fermi energy of graphene, and also the incident angle. By optimizing the structural parameter of this structure, the giant spin shift (almost equal to its upper limit, half of the incident beam waist) in broadband range is achieved, covering the terahertz, infrared, and visible range. The difference is that in the terahertz region, the Brewster angle corresponding to the giant spin shift is larger than that of infrared range and visible range. These findings provide us with a convenient and effective way to tune the photonic SHE, and may offer an opportunity for developing new tunable photonic devices in broadband range. [ABSTRACT FROM AUTHOR]

We theoretically propose a reconfigurable two-dimensional (2D) hexagonal sonic crystal with higher-order topology protected by the six-fold, C6, rotation symmetry. The acoustic band gap and band topology can be controlled by rotating the triangular scatterers in each unit cell. In the nontrivial phase, the sonic crystal realizes the topological spin Hall effect in a higher-order fashion: (i) the edge states emerging in the bulk band gap exhibit partial spin-momentum correlation and are gapped due to the reduced spatial symmetry at the edges. (ii) The gapped edge states, on the other hand, stabilize the topological corner states emerging in the edge band gap. The partial spin-momentum correlation is manifested as pseudo-spin-polarization of edge states away from the time-reversal invariant momenta, where the pseudospin is emulated by the acoustic orbital angular momentum. We reveal the underlying topological mechanism using a corner topological index based on the symmetry representation of the acoustic Bloch bands. [ABSTRACT FROM AUTHOR]

The latest research suggests that strain can be utilized to engineer the electronic states of Weyl semimetals (WSMs) through creating a pseudo-magnetic field B _el . The response of strained WSMs to a real time-varying electric field E with E ⊥ B _el can cause spatial chirality and charge separation in WSMs, i.e., the chiral Hall effect (CHE). Herein, the photonic spin Hall effect (PSHE) modified by CHE in strained WSM thin films is studied. We show that the in-plane and transverse photonic spin-dependent shifts (⟨Δ x _+ ⟩ and ⟨Δ y _+ ⟩) can be tuned to be more than 400 and 50 times of incident wavelength, respectively, at the angular frequency being close to the cyclotron frequency of massless fermions in the pseudo-magnetic field. In order to enhance the PSHE, epsilon-near-zero materials take priority of being as the substrates of WSM films. Besides, both ⟨Δ x _+ ⟩ and ⟨Δ y _+ ⟩ generally give extreme values around incident angles at which Fresnel reflection coefficients exhibit local minimums, whereas an inversion-symmetry breaking with nonzero axial chemical potential may break this generality. Finally, one possible experimental strategy for observing this CHE tuned PSHE is schemed, which may provide a pristine optical technique to precisely engineer and detect the strain in topological materials.

We unveil that the holey graphyne (HGY), a two-dimensional carbon allotrope where benzene rings are connected by two −C≡C− bonds fabricated recently in a bottom-up way, exhibits topological electronic states. Using first-principles calculations and Wannier tight-binding modeling, we discover a higher-order topological invariant associated with C 2 symmetry of the material, and show that the resultant corner modes appear in nanoflakes matching to the structure of precursor reported previously, which are ready for direct experimental observations. In addition, we find that a band inversion between emergent g -like and h -like orbitals gives rise to a nontrivial topology characterized by Z 2 invariant protected by an energy gap as large as 0.52 eV, manifesting helical edge states mimicking those in the prominent quantum spin Hall effect, which can be accessed experimentally after hydrogenation in HGY. We hope these findings trigger interests towards exploring the topological electronic states in HGY and related future electronics applications. [ABSTRACT FROM AUTHOR]

The photonic spin Hall effect (SHE) provides an effective way to manipulate the spin-polarized photons. However, the spin-dependent splitting is very tiny due to the weak spin–orbit coupling, and previous investigations for enhancing this phenomenon have some serious limitations (e.g. inconvenient to tune, inadequate attention in terahertz region). Therefore, controlling and enhancing the photonic SHE in a flexible way is highly desirable, especially for terahertz region. In this contribution, we propose a method to manipulate the photonic SHE by taking advantage of tunable optical properties of graphene via weak optical pumping. We find that photonic SHE of graphene-dielectric structure in terahertz region is quite sensitive to the pumping power. The spin shift for H polarized incident beam can reach its upper limitation under the optimal pumping power, which is related to the zero value of the real part of graphene conductivity. These findings may provide a new degree of freedom for the design of tunable spin-based photonic devices in the future. [ABSTRACT FROM AUTHOR]

Canted antiferromagnets offer great potential in fundamental research and for use in applications due to their unique properties. The presence of the Dzyaloshinskii–Moriya interaction (DMI) leads to the existence of a weak ferromagnetic moment at room temperature. We study both theoretically and experimentally microwave spin pumping by a quasi-ferromagnetic mode from a canted easy plane antiferromagnet with weak ferromagnetism FeBO3. The conversion of a microwave signal into a constant voltage is realized using the inverse spin Hall effect in an iron borate/heavy metal heterostructure. We use an additional bias magnetic field to selectively tune the resonance frequency of such a microwave detector over a wide range up to 43.5 GHz with a potential sensitivity near 2.5 µ V W−1. We confirm the pure spin current nature by changing the polarity of the detected via inverse spin Hall effect voltage by switching the direction of the bias magnetic field. We believe that our results will be useful for the development of highly tunable, portable and sensitive microwave antiferromagnet-based functional devices. [ABSTRACT FROM AUTHOR]

The photonic spin Hall effect (SHE) provides an effective way to manipulate the spin-polarized photons. However, the spin-dependent splitting is very tiny due to the weak spin–orbit coupling, and previous investigations for enhancing this phenomenon have some serious limitations (e.g. inconvenient to tune, inadequate attention in terahertz region). Therefore, controlling and enhancing the photonic SHE in a flexible way is highly desirable, especially for terahertz region. In this contribution, we propose a method to manipulate the photonic SHE by taking advantage of tunable optical properties of graphene via weak optical pumping. We find that photonic SHE of graphene-dielectric structure in terahertz region is quite sensitive to the pumping power. The spin shift for H polarized incident beam can reach its upper limitation under the optimal pumping power, which is related to the zero value of the real part of graphene conductivity. These findings may provide a new degree of freedom for the design of tunable spin-based photonic devices in the future.

The spin Hall effect (SHE), which converts a charge current into a transverse spin current, has long been believed to be a phenomenon induced by spin--orbit coupling. Here, we identify an alternative mechanism to realize the intrinsic SHE through a noncollinear magnetic structure that breaks the spin rotation symmetry. No spin--orbit coupling is needed even when the scalar spin chirality vanishes, different from the case of the topological Hall effect and topological SHE reported previously. In known noncollinear antiferromagnetic compoundsMn3X (X = Ga, Ge, and Sn), for example, we indeed obtain large spin Hall conductivities based on ab initio calculations. [ABSTRACT FROM AUTHOR]

We theoretically investigate the photonic spin Hall effect (PSHE) of graphene hyperbolic metasurfaces in the terahertz region. We demonstrate that the PSHE shifts can reflect the topological transition of metasurfaces through tuning the frequency of the incident light or the Fermi energy of graphene. The PSHE shifts vary with rotating hyperbolic metasurfaces and arrive at the maximum when the electric field direction of the incident polarized light is along graphene strips. The PSHE shift component, the Goos–Hänchen shift, is enhanced by the orbital angular momentum, which can be used to identify the topologic charge of the Laguerre–Gaussian beam. Barcode encryption utilizing the PSHE shifts is illustrated, which has potential application in information processing. [ABSTRACT FROM AUTHOR]

This is an update of a previous review (Naumis et al 2017 Rep. Prog. Phys. 80 096501). Experimental and theoretical advances for straining graphene and other metallic, insulating, ferroelectric, ferroelastic, ferromagnetic and multiferroic 2D materials were considered. We surveyed (i) methods to induce valley and sublattice polarisation (P) in graphene, (ii) time-dependent strain and its impact on graphene's electronic properties, (iii) the role of local and global strain on superconductivity and other highly correlated and/or topological phases of graphene, (iv) inducing polarisation P on hexagonal boron nitride monolayers via strain, (v) modifying the optoelectronic properties of transition metal dichalcogenide monolayers through strain, (vi) ferroic 2D materials with intrinsic elastic (σ), electric (P) and magnetic (M) polarisation under strain, as well as incipient 2D multiferroics and (vii) moiré bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The update features the experimental realisations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of elemental 2D ferroelectric bismuth, and 2D multiferroic NiI2. The document was structured for a discussion of effects taking place in monolayers first, followed by discussions concerning bilayers and few-layers, and it represents an up-to-date overview of exciting and newest developments on the fast-paced field of 2D materials. [ABSTRACT FROM AUTHOR]

Photoexcitation and shaping of a propagating surface plasmon polariton (SPP) on silver and gold microstructures are well established and lead to the discovery of the plasmonic spin-Hall effect recently. Whereas silver is often the material of choice due to its exceptional low plasma frequency and weak damping, similar observations have not been reported for ferromagnetic metals. In this work, we report on propagating SPPs on Ni _80 Fe _20 microstructures imaged by photoemission electron microscopy (PEEM) in combination with a tunable femtosecond laser system at MHz repetition rate. Circular dichroic (CD) images in threshold PEEM show clear edge-induced SPPs with sub-micrometer wavelength and propagation length of about 3.5 μ m. Analysis of the interference patterns as well as the coupling of the optical spin angular momentum to the observed fringe fields reveal propagation characteristics exclusive to evanescent waves and the presence of the plasmonic spin-Hall effect. Our work provides direct evidence that many materials with a high plasma frequency allow for excitation and observation of propagating SPPs at the dielectric/metal interface via CD PEEM imaging, enabling magnetoplasmonic investigation of common ferromagnets on nanometer length and femtosecond time scales.

The thermo-spin conversion provides new concepts for further developing the green energy-harvesting technology because spin can be controlled with minimal energy in nanostructures. Through theoretical analysis of thermo-spin generation, transportation and conversion in ferromagnet/non-ferromagnet/heavy metal (FM/NM/HM) vertical structures, we found that the output transverse thermo-spin voltage is independent of the structure's width, but varies linearly with the structure's length. To validate our predictions, we fabricated the thermo-spin devices with a CoFeAl/Cu/Pt structure. Our results indicate that FM/NM/HM structures can be utilized to design flexible thermo-spin conversion devices. [ABSTRACT FROM AUTHOR]

Quantum spin Hall (QSH) effect, a fundamentally new quantum state of matter and topological phase transitions are characteristics of a kind of electronic material, popularly referred to as topological insulators (TIs). TIs are similar to ordinary insulator in terms of their bulk bandgap, but have gapless conducting edge-states that are topologically protected. These edge-states are facilitated by the time-reversal symmetry and they are robust against nonmagnetic impurity scattering. Recently, the quest for new materials exhibiting non-trivial topological state of matter has been of great research interest, as TIs find applications in new electronics and spintronics and quantum-computing devices. Here, we propose and demonstrate as a proof-of-concept that QSH effect and topological phase transitions can be realized in ${\mathrm{InN}}_{x}{\mathrm{Bi}}_{y}{\mathrm{Sb}}_{1-x-y}$ /InSb semiconductor quantum wells (QWs). The simultaneous incorporation of nitrogen and bismuth in InSb is instrumental in lowering the bandgap, while inducing opposite kinds of strain to attain a near-lattice-matching conducive for lattice growth. Phase diagram for bandgap shows that as we increase the QW thickness, at a critical thickness, the electronic bandstructure switches from a normal to an inverted type. We confirm that such transition are topological phase transitions between a traditional insulator and a TI exhibiting QSH effect—by demonstrating the topologically protected edge-states using the bandstructure, edge-localized distribution of the wavefunctions and edge-state spin-momentum locking phenomenon, presence of non-zero conductance in spite of the Fermi energy lying in the bandgap window, crossover points of Landau levels in the zero-mode indicating topological band inversion in the absence of any magnetic field and presence of large Rashba spin-splitting, which is essential for spin-manipulation in TIs.

We systematically study the stationary and precessional states in a uniaxial antiferromagnet under the dampinglike spin–orbit torque (SOT). The stable regions for all equilibria are defined by the linear stability analysis. In the regions without any stable equilibrium, we confirm that a stable conical precession may exist. Invoking symmetry arguments, we rigorously reduce the coupled Landau–Lifshitz–Gilbert equations to a single-vector one, which allows us to derive the analytic expressions of the lower and upper thresholds, the frequency, and the amplitude of precession for a weak uniaxial anisotropy. Its frequency is of the order of THz and increases almost linearly with the current. Further analysis reveals that the precession is mainly propelled by the exchange interaction in the promise that the SOT balances the damping one in average. Moreover, the investigation uncovers that a weak anisotropy can improve the frequency tunability, and a small damping benefits lowering the exciting current. Finally, the analytic expressions are verified by comparing with numerical simulations of the original Landau–Lifshitz–Gilbert equations.

This document is an editorial from the journal Nanotechnology titled "Multi-physics coupling in nanoscale spintronics and quantum devices." It discusses the importance of exploring the physical properties and applications of quantum devices, particularly in relation to their coupling with external fields such as electric field, strain, and temperature. The editorial introduces a focus collection of 13 research articles that present the multi-physics coupling of various properties of quantum materials and devices. The articles cover topics such as enhancing the coherence of plasmon-emitter strong coupling systems, theoretical concepts of quantum anomalous Hall effect and quantum spin Hall effect, effects of organic molecules on the properties of 2D materials, and the impact of edge reconstruction and grain boundaries on the properties of nanoribbons and black phosphorene structures. The editorial concludes by expressing gratitude to the authors and the editorial team and hopes that readers will enjoy the collection. [Extracted from the article]

We show that spin–orbit interaction and elastic spin-Hall effect can exist in a classical mechanical system consisting of a two-dimensional honeycomb lattice of masses and springs. The band structure shows the presence of splitting at K point induced by the difference of longitudinal and transverse elastic constant, and this splitting can be regarded as an effective Dresselhaus-type spin–orbit coupling. Interestingly, as an initial displacement away from the equilibrium is applied, the time evolution simulation shows that waves of different spin polarization propagates along different directions at the Γ and K point, which is characteristic of spin-Hall effect. Several cases for spin-Hall effect are also discussed.