Orbitronics is based on the use of orbit currents as information carriers. Up to now, orbit currents were created from the conversion of charge or spin currents, and inversely, they could be converted back to charge or spin currents. Here we demonstrate that orbit currents can also be generated by femtosecond light pulses on Ni. In multilayers associating Ni with oxides and nonmagnetic metals such as Cu, we detect the orbit currents by their conversion into charge currents and the resulting terahertz emission. We show that the orbit currents extraordinarily predominate the light-induced spin currents in Ni-based systems, whereas only spin currents can be detected with CoFeB-based systems. In addition, the analysis of the time delays of the terahertz pulses leads to relevant information on the velocity and propagation of orbit carriers. Our finding of light-induced orbit currents and our observation of their conversion into charge currents opens new avenues in orbitronics, including the development of orbitronic terahertz devices.
Recent progress in orbitronics reveals the possibility of using orbit current as an information carrier. The interconversion between orbit currents and charge currents is crucial for orbit information processing. Although orbit currents can be created from charge currents via the orbital Hall effect, the conversion from orbit currents into charge currents has been observed only in very few systems due to the lack of a reliable orbit current source and the disturbance of the omnipresent inverse spin Hall effect. In this study, we show that ultrafast pulses of orbit current can be generated in N…
In solids, electronic Bloch states are formed by atomic orbitals. While it is natural to expect that orbital composition and information about Bloch states can be manipulated and transported, in analogy to the spin degree of freedom extensively studied in past decades, it has been assumed that orbital quenching by the crystal field prevents significant dynamics of orbital degrees of freedom. However, recent studies reveal that an orbital current, given by the flow of electrons with a finite orbital angular momentum, can be electrically generated and transported in wide classes of materials des…
Spintronics is showing promising results in the search for new materials and effects to reduce energy consumption in information technology. Among these materials, ferrimagnets are of special interest, since they can produce large spin currents that trigger the magnetization dynamics of adjacent layers or even their own magnetization. Here, we present a study of the generation of spin current by GdFeCo in a GdFeCo/Cu/NiFe trilayer where the FeCo sublattice magnetization is dominant at room temperature. Magnetic properties such as the saturation magnetization are deduced from magnetometry measu…
Graphene-based superlattices offer a new materials playground to exploit and control a higher number of electronic degrees of freedom, such as charge, spin, or valley for disruptive technologies. Recently, orbital effects, emerging in multivalley band structure lacking inversion symmetry, have been discussed as possible mechanisms for developing orbitronics. Here, we report non-local transport measurements in small gap hBN/graphene/hBN moiré superlattices which reveal very strong magnetic field-induced chiral response which is stable up to room temperature. The measured sign dependence of the …
Nonlocal Electrical Detection of Reciprocal Orbital Edelstein Effect
The University of Tokyo（东京大学）；RIKEN（理化学研究所）；National Institute of Advanced Industrial Science and Technology (AIST)（国立先进工业科学技术研究院）；Pohang University of Science and Technology（浦项科技大学）；Korea Advanced Institute of Science and Technology（韩国科学技术院）；Johannes Gutenberg University Mainz（美因茨约翰内斯古腾堡大学）；Forschungszentrum Jülich（于利希研究中心）
Terahertz switching of antiferromagnetic order by Néel spin-orbit torques
Freie Universität Berlin（柏林自由大学）；Fritz-Haber Institute of the Max Planck Society（马克斯·普朗克学会弗里茨·哈伯研究所）；Johannes Gutenberg-Universität Mainz（美因茨约翰内斯·古腾堡大学）；University of Konstanz（康斯坦茨大学）
Current-induced spin-orbit torque (SOT) is regarded as a promising mechanism for driving neuromorphic behavior in spin-orbitronic devices. In principle, the strong SOT in heavy metal-based magnetic heterostructure is attributed to the spin-orbit coupling (SOC)-induced spin Hall effect (SHE) and/or the spin Rashba-Edelstein effect (SREE). Recently, SOC-free mechanisms such as the orbital angular momentum (OAM)-induced orbital Hall effect (OHE) and/or the orbital Rashba-Edelstein effect (OREE) have been proposed to generate sizable torques comparable to those from the conventional spin Hall mech…
Iridium is a very promising material for spintronic applications due to its interesting magnetic properties such as large RKKY exchange coupling as well as its large spin-orbit coupling value. Ir is for instance used as a spacer layer for perpendicular synthetic antiferromagnetic or ferrimagnet systems. However, only a few studies of the spintronic parameters of this material have been reported. In this paper, we present inverse spin Hall effect - spin pumping ferromagnetic resonance measurements on CoFeB/Ir based bilayers to estimate the values of the effective spin Hall angle, the spin diffu…
Antiferromagnets host exotic quasiparticles, support high frequency excitations and are key enablers of the prospective spintronic and spin-orbitronic technologies. Here, we propose a concept of a curvilinear antiferromagnetism where material responses can be tailored by a geometrical curvature without the need to adjust material parameters. We show that an intrinsically achiral one-dimensional (1D) curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable Dzyaloshinskii--Moriya interaction (DMI) and orientation of the Néel vector. The curvature-induced DMI results …
Spin-orbitronics at a topological insulator-semiconductor interface
拓扑绝缘体由于其表面态的自旋织构，在新的自旋相关现象和应用方面有着巨大的潜力。然而，由于这些材料难以与主流硅基技术集成，因此仍然缺乏允许利用这些资产的通用平台。在这里，我们利用锗作为生长的Bi $_2$ Se $_3$，一个原型TI的衬底。我们通过非局域探测方法研究了Bi $_2$ Se $_3$ /Ge原始界面的自旋-电荷转换.自旋布居由Ge中的光学取向产生，并且朝向充当自旋检测器的Bi $_2$ Se $_3$扩散。我们比较了Bi $_2$ Se $_3$ /Ge和Pt在相同实验条件下的自旋-电荷转换。值得注意的是，由TI检测器给出的自旋-电荷转换的符号与Pt检测器相比是相反的，而效率是相当的。利用第一性原理计算，我们归因于符号反转的杂化的拓扑表面状态的Bi $_2$ Se $_3$与Ge带。这些结果铺平了道路，实现高效的自旋检测TI为基础的架构与基于磁阻电机的平台兼容。
Terahertz spintronics offers the prospect of devices which are both faster and more energy-efficient. A promising route to achieve this goal is to exploit current-induced spin-orbit torques. However, the high-frequency properties of these quantities remain unexplored both experimentally and theoretically, within a realistic material-specific approach. Here we investigate the dynamical transverse components of the torques and uncover contributions longitudinal to the magnetic moment capable of changing its magnitude. We show that, while the torques can be drastically altered in the dynamical re…
We investigate the effect of Rashba spin-orbit coupling (SOC) on the optoelectronic properties of n- and p-type monolayer MoS2. The optical conductivity is calculated within the Kubo formalism. We find that the spin-flip transitions enabled by the Rashba SOC result in a wide absorption window in the optical spectrum. Furthermore, we evaluate the effects of the polarization direction of the radiation, temperature, carrier density, and the strength of the Rashba spin-orbit parameter on the optical conductivity. We find that the position, width, and shape of the absorption peak or absorption wind…
Spectroscopic confirmation of linear relation between Heisenberg- and interfacial Dzyaloshinskii-Moriya-exchange in polycrystalline metal films
新的自旋轨道逻辑1和存储设备2的建议通常是基于假设，即具有大自旋轨道耦合的材料在接触时如何与铁磁体相互作用。这种相互作用产生了一系列新的现象，如自旋-轨道矩3，4，手性自旋结构5，6和手性自旋矩。这些手性性质与反对称交换有关，也称为界面Dzyaloshinskiii-Moriya相互作用（Dzyaloshinskiii-Moriya interaction）（Dzyaloshinskiii-Moriya interaction）9，10。对于许多现象来说，对称海森堡交换和量子交换的相对强度非常重要。在这里，我们使用光学自旋波光谱（布里渊光散射），以直接确定一系列的Ni 80 Fe 20/Pt样品的π矢量，然后比较最近邻π耦合能量与独立测量的海森堡交换积分。我们发现微观对称交换和反对称交换的Ni 80 Fe 20厚度依赖性是相同的，这与Moriya最初提出的基本机制基本上共享相同的基础物理的概念一致。虽然具有重要的基础重要性，但这一结果也使我们更深入地了解了自旋轨道电子的应用，以及如何优化它。
Persistent, oscillatory charge and spin currents are shown to be driven by a two-component terahertz laser pulse in a one-dimensional mesoscopic ring with Rashba-Dresselhaus spin orbit interactions (SOI) linear in the electron momentum. The characteristic interference effects result from the opposite precession directions imposed on the electron spin by the two SOI couplings. The time dependence of the currents is obtained by solving numerically the equation of motion for the density operator, which is later employed in calculating statistical averages of quantum operators on few electron eige…
While current-induced torque by orbital current has been experimentally found in various structures, evidence for its reciprocity has been missing so far. Here, we report experimental evidence of strong inverse orbital torque in YIG/Pt/CuOx (YIG = Y3Fe5O12) mediated by spin-orbital entangled electronic states in Pt. By injecting spin current from YIG to Pt by the spin pumping via ferromagnetic resonance and by the spin Seebeck effect, we find a pronounced inverse spin Hall effect-like signal. While a part of the signal is explained as due to the inverse spin-orbital Hall effect in Pt, we also …
Phase transition and current of planar clusters with loops of Josephson $π$ junction is of great importance for application in the adiabatic quantum computation devices (AQC). Each $π$-ring possesses an orbital moment with a current. The orientation of these orbital moments is altered by self-interactions and controlled with a bias current. In the current research, we construct the phase diagram of semi-hydrogenated SiB (H-SiB) semiconductor using a two-dimensional (2D) Ising model with considering nearest-neighbor and diagonal interactions of spin planes on the on the hexagonal lattice. Our f…
Spin torques are at the heart of spin manipulations in spintronic devices. Here, we examine the existence of an optical spin-orbit torque, a relativistic spin torque originating from the spin-orbit coupling of an oscillating applied field with the spins. We compare the effect of the nonrelativistic Zeeman torque with the relativistic optical spin-orbit torque for ferromagnetic systems excited by a circularly polarised laser pulse. The latter torque depends on the helicity of the light and scales with the intensity, while being inversely proportional to the frequency. Our results show that the …
We study the charge and spin dependent scattering in a set of CoFeB thin films whose crystalline order is systematically enhanced and controlled by annealing at increasingly higher temperatures. Terahertz conductivity measurements reveal that charge transport closely follows the development of the crystalline phase, with increasing structural order leading to higher conductivity. The terahertz-induced ultrafast demagnetization, driven by spin-flip scattering mediated by the spin-orbit interaction, is measurable in the pristine amorphous sample and much reduced in the sample with highest crysta…
Terahertz radiation-induced conductivity, Kerr and Faraday angles, and spin textures in a two-dimensional electron gas with spin-orbit coupling subjected to a high magnetic field and periodic potential
Efficient generation of spin-orbit torques (SOTs) is central for the exciting field of spin-orbitronics. Platinum, the archetypal spin Hall material, has the potential to be an outstanding provider for spin-orbit torques due to its giant spin Hall conductivity, low resistivity, high stabilities, and the ability to be compatible with CMOS circuits. However, pure clean-limit Pt with low resistivity still provides a low damping-like spin-orbit torque efficiency, which limits its practical applications. The efficiency of spin-orbit torque in Pt-based magnetic heterostructures can be improved consi…
Modern spintronics relies on the generation of spin currents through spin-orbit coupling. The spin-current generation has been believed to be triggered by current-induced orbital dynamics, which governs the angular momentum transfer from the lattice to the electrons in solids. The fundamental role of the orbital response in the angular momentum dynamics suggests the importance of the orbital counterpart of spin currents: orbital currents. However, evidence for its existence has been elusive. Here, we demonstrate the generation of giant orbital currents and uncover fundamental features of the o…
