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Abstract Unidirectional spin Hall magnetoresistance (USMR) has emerged as a promising candidate for magnetoresistive random-access memory (MRAM) technology. However, the realization of high signal-to-noise output signal in USMR devices has remained a challenge, primarily due to the limited USMR effect at room temperature. In this study, we report a large USMR effect in FeNi/Pt/Bi₂Se₃ trilayers through interfacial engineering with Pt to optimize the spin current transmission efficiency and electron-magnon scattering. Our devices exhibit a USMR value that is an order of magnitude higher than previously reported systems, reaching 30.6 ppm/MA/cm² at room temperature. First-principles calculations and experimental observations suggest that the Pt layer not only preserves the spin-momentum locked topological surface states in Bi₂Se₃ at the Fermi-level but also generates additional Rashba surface states within the Pt itself to enhance the effective SOT efficiency. Furthermore, we demonstrate that the two-terminal USMR-MRAM devices show robust output performance with 2nd harmonic resistance variation around 0.11 Ω/mA. Remarkably, the performance of these devices further improves at elevated temperatures, highlighting their potential for reliable operation in a wide range of environmental conditions. Our findings pave the way for future advancements in high-performance, energy-efficient spintronic memory devices.

Abstract Through pumping a spin current from ferromagnet into heavy metal (HM) via magnetization precession, parts of the injected spins are in-plane rotated by the lattice vibration, namely acoustic spin rotation (ASR), which manifests itself as an inverse spin Hall voltage in HM with an additional 90° difference in angular dependency. When reversing the stacking order of bilayer with a counter-propagating spin current or using HMs with an opposite spin Hall angle, such ASR voltage shows the same sign, strongly suggesting that ASR changes the rotation direction due to interface spin-orbit interaction. With the drift-diffusion model of spin transport, we quantify the efficiency of ASR up to 30%. The finding of ASR endows the acoustic device with an ability to manipulate spin, and further reveals a new spin-orbit coupling between spin current and lattice vibration.

Abstract Gas‐insulated switchgears (GIS) are crucial components of high‐voltage power transmission and distribution systems. Internal discharges within GIS have garnered significant attention in the field of power engineering. This study investigates the characteristics of internal discharge shock waves in GIS under an air pressure of 0.3 MPa and three different discharge gap conditions: 1, 1.5, and 2 mm. High‐speed shadowing techniques are used to analyse the propagation speed, morphology, and post‐wave parameters. The study findings reveal that although the characteristics of internal discharge shock waves in GIS noticeably change with the gap size, they also exhibit a consistent trend: as the gap size increases, the initial shock wave accelerates, intensifying the discharge. Simultaneously, the rate of attenuation rises, with the shock wave becoming weaker after ≈30 µs. Furthermore, the post‐wave parameters follow a similar pattern, with an increase in gap size leading to higher parameter values but also a faster decay rate. The parameters decay more rapidly between 10 and 20 µs, slow down between 20 and 30 µs, and ultimately stabilize after around 30 µs. The results of this study hold significant theoretical and practical implications for the monitoring, diagnosis, and prevention of internal discharges in GIS.

Abstract The gas‐insulated switchgear (GIS) is a vital component of a power system, and understanding the shock wave characteristics of its internal discharge is crucial to ensure the safe and stable operation of the entire system. In this study, a high‐speed shadowing technique is employed to obtain the shadowgraphs of a typical flow‐field evolution of sulfur hexafluoride (SF6) gas following the breakdown of a pin–plate gap inside a GIS. Experimental data were used to derive parameters, including the Mach number, propagation speed, distance of the discharge shock wave, and the temperature, pressure, density, and velocity of the SF6 gas after wave generation. With a 0.2‐mm discharge gap and 0.4‐MPa pressure, the discharge generates a spherical shock wave, centred at the contact between the discharge channel and electrodes, that propagates in all directions. The shock wave gradually weakens after 20 μs, propagating at near‐sonic speed, and its Mach number decreases from 2.92 to 1.15; similarly, its post‐wave parameters sharply decrease during the first 20 μs. Additionally, a significant reflection occurs when the shock wave propagates to the metal wall. The authors’ findings provide a valuable reference for detecting and diagnosing the internal discharge in GISs.

The search for room-temperature superconductors has been a long-standing goal in condensed matter physics. In this study, we investigate the electronic and geometric properties of lead apatite with and without Cu doping within the framework of the density functional theory. Based on our calculations, we found that without Cu doping, the lead apatite PPOO shows an insulator character with flatbands that straddle the Fermi level. Once we introduce O1 vacancies, the flatbands disappear. Furthermore, we analyze the effects of Cu doping on the crystal structure and the electronic band structure of the material PCPOO4. Our calculations reveal the presence of one-dimensional channels induced by fully occupied O1 atoms that are only 1/4 occupied in the literature, which may play a crucial role in the realization of room-temperature superconductivity. Based on our findings, we propose a possible solution to improve the quality of superconductivity by annealing the material in an oxygen atmosphere. These results contribute to a better understanding of the unusual properties of Cu-doped lead apatite PCPOO4 and will pave the way for further exploration of its potential as a room-temperature superconductor.

Abstract Klein tunneling associated with particle-antiparticle pair productions across a potential barrier is a key prediction of quantum-field theory for relativistic particles. Yet, a direct experimental realization is hampered by the particles large rest mass resulting in high potential barrier. Here, for non-Hermitian antiferromagnets, at the verge of the anti-parity-time symmetry transition, chiral magnons are demonstrated to offer a bosonic platform to access Klein tunneling at meV energies in experimentally feasible settings. Our analytical and numerical simulations evidence that magnetic damping renders a low energy mechanism for the breakdown of the magnonic vacuum and for creating particle-antiparticle pairs in strong magnetic fields. Adopting Feynman’s picture for antiparticles, the tunneling time of an incident magnon wave packet across a supercritical barrier is found to be negative. The uncovered aspects point to the potential of chiral magnons for addressing fundamental physics in a conceptually simple setup with the potential for use in chirality-dependent magnonic computing.

Abstract To locate the ground encroachments in transmission line corridor effectively, the application of a novel binocular stereo vision (BSV) for distance measurement is realized with improvement and adjustment in calibration and reconstruction process of BSV. Firstly, a calibration method using a 1‐D pole with spatial constraints to replace the 2‐D calibration object is proposed. The field experiment shows that this method improves the accuracy of the calibration in a large‐scale scene by expanding the calibration area. Then, a regulation algorithm to eliminate the difference between focal lengths for binocular cameras is designed to further improve accuracy of calibration. For practical utilization of BSV in the monitor system, the 3‐D reconstructions from world coordinate system (WCS) to ground‐based system is achieved by rotation and transformation of the reconstructed coordinate system and direct height measurement is realized consequently. Further, based on the calibration method being proposed, the partial calibration with a reduced calibration distribution area is studied considering the probable complex terrain. Height measurement calculations are carried out on both hypothetical and real obstacles to verify the validity of the calibration method and postprocessing algorithms. The results demonstrated that the calibration method algorithms successfully realized the practical application of BSV in large‐scale scene with high accuracy. By using this novel BSV technology, the total transmission line inspection cost is expected to be greatly reduced by comparing with manned helicopter and UAV inspections.

The spin Hall effect (SHE), typically emerging in non-magnetic metals with strong spin-orbit couplings, has attracted significant attention for its ability to convert a charge current into a spin current, a key feature in power-efficient spintronic devices. Recently, an enhanced SHE has been detected in the magnetic alloys, where the spin Hall conductivity is strongly modified by the dynamical and thermal spin fluctuations. We find that the spin Hall angle ( ${\theta _{{\text{SH}}}}$ ) in Pt _100− _x Co _x alloys dramatically changes at the Curie temperature, which is positive in the paramagnetic phase akin to Pt, while negative in the ferromagnetic phase. Such intriguing behavior of ${\theta _{{\text{SH}}}}$ stemming from individual and collective fluctuations in the magnetic moments is further substantiated with the full-fledged Monte Carlo simulations. Our work broadens insights into the SHE and highlights the importance of spin fluctuations for the spin-current generation near the ferromagnetic instability point of magnetic alloys.

Dzyaloshinskii–Moriya (DM) interactions cause many interesting physical features, such as topologically nontrivial magnetic skyrmions and chiral domain walls. These interactions become more pronounced in low-dimensional systems. We investigated a one-dimensional Heisenberg spin-1/2 chain with an asymmetric DM interaction. The results show that, upon applying a nonzero DM interaction, the Néel ground state transitions to a spin chiral phase. Moreover, using the mean-field approximation, we obtain the dispersion of the energy spectrum, from which the z-axis spin chirality is calculated as a function of the strength of the DM interaction for low-lying excitations. The results indicate that the DM interaction facilitates chirality for Dz ≤ J and induces a spin-gapped chiral state.

We consider the propagation of phonons in the presence of a particle sink with radial flow in a Bose–Einstein condensate. Because the particle sink can be used to simulate a static acoustic black hole, the phonon would experience a considerable spacetime curvature at appreciable distance from the sink. The trajectory of the phonons is bended after passing by the particle sink, which can be used as a simulation of the gravitational lensing effect in a Bose–Einstein condensate. Possible experimental implementations are discussed.

Abstract Antiferromagnetic (AFM) materials offer an exciting platform for ultrafast information handling with low cross-talks and compatibility with existing technology. Particularly interesting for low-energy cost computing is the spin wave-based realization of logic gates, which has been demonstrated experimentally for ferromagnetic waveguides. Here, we predict chiral magnonic eigenmodes with a finite intrinsic, magnonic orbital angular momentum ℓ in AFM waveguides. ℓ is an unbounded integer determined by the spatial topology of the mode. We show how these chiral modes can serve for multiplex AFM magnonic computing by demonstrating the operation of several symmetry- and topology-protected logic gates. A Dzyaloshinskii–Moriya interaction may arise at the waveguide boundaries, allowing coupling to external electric fields and resulting in a Faraday effect. The uncovered aspects highlight the potential of AFM spintronics for swift data communication and handling with high fidelity and at a low-energy cost.

Skyrmions hold great promise in future spintronics applications since they are robust against local deformations. The meron, due to its topological equivalence to a half skyrmion, has been widely found to appear in pairs. Motivated by recent progresses in high-spin Kitaev magnets, here we investigate numerically a classical Kitaev-Γ model with a single-ion anisotropy. An exotic spin texture consisting of three merons is discovered. Such a state features a peculiar property with an odd number of merons in one magnetic unit cell. Therefore, these merons cannot be dissociated from skyrmions as reported in the literature and their origin is briefly discussed. Moreover, we find that these three merons contribute a finite topological number and thus it can induce the topological Hall effect (THE). Experimentally this spin texture can be observed by the Lorentz transmission electron microscopy and the THE can be used to identify the finite topological number. Our work demonstrates that high-spin Kitaev magnets can host robust unconventional spin textures and thus they offer a versatile platform for exploring exotic spin textures as well as their applications in spintronics.

The optimized concentration of SF6 gas is the key to maintaining a good insulation performance by GIS equipment. The precise measurements of the SF6 concentration and decomposition byproducts could be used to indicate the remaining GIS insulation level during long-term operations. In this paper, a finite-element simulation model was created to investigate the SF6 gas decomposition and diffusion dynamics. A theoretical analysis and simulation of the overheating fault, i.e., the contact between the GIS disconnect switches, were carried out, followed by an estimation of the SF6 decomposition and diffusion characteristics caused by the local heating faults, based on the calculated flow velocity field and temperature field.

The magnonic currents promise the opportunity for the energy efficient information processing and communication technologies. Here the authors theoretically show the propagating spin waves that carry orbital angular momentum can be electrically tunable and protected against damping in a cylindrical magnetic insulator waveguide.

We study the impact of the transition across the anti-parity-time (anti- $\mathcal{PT}$ ) symmetry breaking point on the low-energy spin excitations in a synthetic antiferromagnet (SyAFM) that consists of two magnetic layers coupled antiferromagnetically via the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction. When varying the interlayer (RKKY) coupling strength a degeneracy point (exceptional point) is reached beyond which the system enters the anti- $\mathcal{PT}$ symmetry-broken phase. This phase is marked by the emergence of a finite net magnetization and low-lying excitations beyond the Goldstone modes in the anti- $\mathcal{PT}$ symmetry-preserved phase. For systems hosting an interfacial Dzyaloshinskii–Moriya interaction, we find a bound state in the continuum with a maximal coherent superposition of SyAFM excitations without any radiation. Analytical results for linearized models are corroborated with full numerical micromagnetic simulations endorsing the robustness and generalities of the theory predictions.

We study the transport and the superconducting dynamics in a layer of type II superconductor (SC) with a normal top layer that hosts a helical magnetic ordering that gives rise to spin-current-driven ferroelectric polarization. Proximity effects akin to this heterostructure result in an anisotropic supercurrent transport and modify the dynamic properties of vortices in the SC. The vortices can be acted upon and controlled by electric gating or other means that couple to the spin ordering in the top layer, which, in turn, alter the superconducting/helical magnet coupling characteristics. We demonstrate, using the time dependent Ginzburg–Landau approach, how the spin helicity of the top layer can be utilized for pinning and guiding the vortices in the superconducting layer.

We report on the dynamics of a Bose–Einstein condensate in one and two dimensions driven by the time-dependent harmonic trapping potential. Without the inter-particle interaction, the condensate exhibits the coherent behavior with the time-oscillating density distribution. When the inter-particle interaction is taken into consideration, the phase fluctuations, the multi-peak structure of the density distribution, and the coherence revival phenomenon, apart from the well-studied density oscillation behavior, can be observed in the condensate. Furthermore, it is demonstrated that due to the dimensional restriction these effects are more stable in the two and three-dimensional system, if compared to the one-dimensional case.

Finite-size effect of the thermal conductivity in one dimensional chain is theoretically investigated with a phenomenological model. Boundary temperature dropping and the spectrum-dependent linear temperature profile within the chain are given self-consistently at high temperatures. A general formula of thermal conductivity is presented and a good agreement with the molecular dynamics simulations is obtained. It is found that while ${\rm{d}}\tfrac{1}{\kappa }/{\rm{d}}\tfrac{1}{{L}}$ decreases with increasing of 1/ L monotonically, the well known linear dependence of thermal resistance 1/ κ on the reciprocal length 1/ L of systems is, however, valid only in two limit cases of $1/L\to \infty $ and/or $1/L\to 0$ .

Herein, we experimentally investigate the effect of temperature on the electric field tunable ferromagnetic resonance (FMR) in a ferroelectric/ferromagnetic heterostructure, and demonstrate the tuning of abnormal change in FMR using the polarization of the ferroelectric layer above 200 K. The FMR was found to be almost unchanged under different electric field strength at 100 K owing to frozen polarization, which causes extremely weak magnetoelectric coupling. More interestingly, negative effective linewidth was observed when an electric field greater than 10 kV/cm was applied above 220 K. The simultaneous electrical control of magnetization and its damping via FMR based on linear magnetoelectric coupling are directly relevant to use of composite multiferroics for a wide range of devices.

After obtaining an exact analytical time-varying solution for the Aharonov–Casher conducting ring embedded in a textured static/dynamic electric field, we investigate the spin-resolved quantum transport in the structure. It is shown that the interference patterns are governed by not only the Aharonov–Casher geometry phase but also the instantaneous phase difference of spin precession through different traveling paths. This dynamic phase is determined by the strength of the applied electric field and can have substantial effects on the charge/spin conductances, especially in the weak field regime as the period of spin precession comparable to that of the orbital motion. Our studies suggest that a low-frequency normal electric field with moderate strength possesses more degrees of freedom for manipulating the spin interference of incident electrons.

We illustrate analytically the formation of vector-spin-chirality bound state due to spin–phonon interaction conditioned by the inverse Dzyaloshinskii–Moriya mechanism. The non-equilibrium dynamics of spin-chirality is effectively mapped into the spin-boson model. For spin-1/2 systems, our study suggests an existence of a gapless first-order phase transition from incoherent to coherent spin fluctuations, which is quantified to an emergence of spin-chirality bound state. The critical strength of spin–phonon interaction is found to be determined by the ratio between the amplitude of spin fluctuations and the Debye frequency of system.

We investigate theoretically the dynamic multiferroic (MF) response of coupled ferroelectric (FE)/ferromagnetic (FM) composites upon excitation by a photo-induced acoustic strain pulse. Two magnetoelectric (ME) mechanisms are considered: interface strain- and charge-mediated ME couplings. The former results in demagnetization, depolarization and repolarization within tens of picoseconds via respectively magnetostriction and piezoelectricity. Charge ME interaction affects the FE/FM feedback response leading to magnetization recovery. Experimental realization based on time-resolved x-ray diffraction is suggested. The findings indicate the potential of composite MF for photo-steered, high-speed, multi-state electronic devices.

Interfacing polar insulating oxides may result in the formation of interface-confined, high density carriers with a number of emergent properties. A local coupling of carriers to a helimagnetic oxide layer is shown to lead to an effective spin-orbit interaction with a band splitting determined by the local s - d exchange interaction. As a result a bias-induced, non-equilibrium long-lived spin density normal to the spiral plane is predicted. We find that the spin accumulation is strongly enhanced when only one of the two bands is at the Fermi level and the chemical potential is close to the band edge. As a consequence we predict a large spin-transfer torque and spin current emission that can be utilized for oxide-based spintronic applications.

Spin transfer nano-oscillators (STNOs) are nanoscale devices which are promising candidates for on-chip microwave signal sources. For application purposes, they are expected to be nano-sized, to have broad working frequency, narrow spectral linewidth, high output power and low power consumption. In this paper, we demonstrate by micromagnetic simulation that magnetic skyrmions, topologically stable nanoscale magnetization configurations, can be excited into oscillation by a spin-polarized current. Thus, we propose a new kind of STNO using magnetic skyrmions. It is found that the working frequency of this oscillator can range from nearly 0 Hz to gigahertz. The linewidth can be smaller than 1 MHz. Furthermore, this device can work at a current density magnitude as small as 10 ^8 A m ^−2 , and it is also expected to improve the output power. Our studies may contribute to the development of skyrmion-based microwave generators.