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The Rashba effect, discovered in 1959, continues to supply fertile ground for fundamental research and applications. It provided the basis for the proposal of the spin transistor by Datta and Das in 1990, which has largely inspired the broad and dynamic field of spintronics. More recent developments include new materials for the Rashba effect such as metal surfaces, interfaces and bulk materials. It has also given rise to new phenomena such as spin currents and the spin Hall effect, including its quantized version, which has led to the very active field of topological insulators. The Rashba effect plays a crucial role in yet more exotic fields of physics such as the search for Majorana fermions at semiconductor-superconductor interfaces and the interaction of ultracold atomic Bose and Fermi gases. Advances in our understanding of Rashba-type spin-orbit couplings, both qualitatively and quantitatively, can be obtained in many different ways. This focus issue brings together the wide range of research activities on Rashba physics to further promote the development of our physical pictures and concepts in this field. The present Editorial gives a brief account on the history of the Rashba effect including material that was previously not easily accessible before summarizing the key results of the present focus issue as a guidance to the reader.

Two hundred years ago, Ampère discovered that electric loops in which currents of electrons are generated by a penetrating magnetic field can mutually interact. Here we show that Ampère’s observation can be transferred to the quantum realm of interactions between triangular plaquettes of spins on a lattice, where the electrical currents at the atomic scale are associated with the orbital motion of electrons in response to the non-coplanarity of neighbouring spins playing the role of a magnetic field. The resulting topological orbital moment underlies the relation of the orbital dynamics with the topology of the spin structure. We demonstrate that the interactions of the topological orbital moments with each other and with the spins form a new class of magnetic interactions − topological–chiral interactions − which can dominate over the Dzyaloshinskii–Moriya interaction, thus opening a path for realizing new classes of chiral magnetic materials with three-dimensional magnetization textures such as hopfions. The motion of electrons in a complex magnetic background may generate novel magnetic interactions. Here, Grytsiuk et al. report that a peculiar orbital motion of electrons in response to a non-coplanarity of neighbouring spins leads to a topological orbital moment, which further gives rise to a new class of magnetic interactions.

Magnetic skyrmions are localized, topologically protected spin structures that have been proposed for storing or processing information due to their intriguing dynamical and transport properties. Important in terms of applications is the recent discovery of interface stabilized skyrmions as evidenced in ultra-thin transition-metal films. However, so far only skyrmions at interfaces with a single atomic layer of a magnetic material were reported, which greatly limits their potential for application in devices. Here we predict the emergence of skyrmions in [4 d /Fe 2 /5 d ] n multilayers, that is, structures composed of Fe biatomic layers sandwiched between 4 d and 5 d transition-metal layers. In these composite structures, the exchange and the Dzyaloshinskii–Moriya interactions that control skyrmion formation can be tuned separately by the two interfaces. This allows engineering skyrmions as shown based on density functional theory and spin dynamics simulations. Materials possessing anisotropic spin exchange interactions can support skyrmion quasiparticle spin textures, which may be exploited in nanomagnetic devices. Here, the authors predict the appearance of skyrmions in multilayered thin films of biatomic Fe sandwiched between 4 d and 5 d transition metals.

A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry-based classification of condensed matter. Exotic spin-transport phenomena, such as the dissipationless quantum spin Hall effect, have been speculated to originate from a topological order whose identification requires a spin-sensitive measurement, which does not exist to this date in any system. Using Mott polarimetry, we probed the spin degrees of freedom and demonstrated that topological quantum numbers are completely determined from spin texture-imaging measurements. Applying this method to Sb and Bi₁₋xSbx, we identified the origin of its topological order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a topological quantum Berry's phase and definite spin chirality, which are the key electronic properties component for realizing topological quantum computing bits with intrinsic spin Hall-like topological phenomena.

Handy for spintronics Chirality, or handedness, occurs when an object differs from its mirror image, and its mirror image cannot superimpose on the original object. Solids with chiral magnetic order could have many useful practical applications, because their novel symmetry allows the mixing of electronic, optical, magnetic and structural properties. Bode et al . have now found evidence for chiral magnetic order in a simple solid-state system: a single layer of manganese atoms on a tungsten substrate. Such chirality could be invaluable in spintronic devices, where spin rather than electron charge is used for data transmission. Spin-polarized scanning tunneling microscopy, where a magnetized tip probes the surface, is used to study an atomic layer of manganese. Magnetic order with a specific chirality is observed; a 'left-rotating' spin spiral structure with a period of about 12 nm. The findings confirm the significance of homochirality for nanoscale magnets, which could play a role in the design novel spintronic devices. Chirality is a fascinating phenomenon that can manifest itself in subtle ways, for example in biochemistry (in the observed single-handedness of biomolecules 1 ) and in particle physics (in the charge-parity violation of electroweak interactions 2 ). In condensed matter, magnetic materials can also display single-handed, or homochiral, spin structures. This may be caused by the Dzyaloshinskii–Moriya interaction, which arises from spin–orbit scattering of electrons in an inversion-asymmetric crystal field 3 , 4 . This effect is typically irrelevant in bulk metals as their crystals are inversion symmetric. However, low-dimensional systems lack structural inversion symmetry, so that homochiral spin structures may occur 5 . Here we report the observation of magnetic order of a specific chirality in a single atomic layer of manganese on a tungsten (110) substrate. Spin-polarized scanning tunnelling microscopy reveals that adjacent spins are not perfectly antiferromagnetic but slightly canted, resulting in a spin spiral structure with a period of about 12 nm. We show by quantitative theory that this chiral order is caused by the Dzyaloshinskii–Moriya interaction and leads to a left-rotating spin cycloid. Our findings confirm the significance of this interaction for magnets in reduced dimensions. Chirality in nanoscale magnets may play a crucial role in spintronic devices, where the spin rather than the charge of an electron is used for data transmission and manipulation. For instance, a spin-polarized current flowing through chiral magnetic structures will exert a spin-torque on the magnetic structure 6 , 7 , causing a variety of excitations or manipulations of the magnetization 8 , 9 and giving rise to microwave emission, magnetization switching, or magnetic motors.

Graphene in spintronics is predominantly considered for spin current leads of high performance due to weak intrinsic spin–orbit coupling of the graphene π electrons. Externally induced large spin–orbit coupling opens the possibility of using graphene in active elements of spintronic devices such as the Das-Datta spin field-effect transistor. Here we show that Au intercalation at the graphene–Ni interface creates a giant spin–orbit splitting (~100 meV) of the graphene Dirac cone up to the Fermi energy. Photoelectron spectroscopy reveals the hybridization with Au 5 d states as the source for this giant splitting. An ab initio model of the system shows a Rashba-split spectrum around the Dirac point of graphene. A sharp graphene–Au interface at the equilibrium distance accounts for only ~10 meV spin–orbit splitting and enhancement is due to the Au atoms in the hollow position that get closer to graphene and do not break the sublattice symmetry. The potential use of graphene in spintronic devices is limited by its weak spin–orbit coupling. Marchenko et al. report an enhancement of the spin splitting in graphene due to hybridization with gold 5 d orbitals, showing a very large Rashba spin–orbit splitting of about 100 meV.

The electronic structure of Fe has been experimentally studied using angle-resolved photoemission spectroscopy (ARPES) since the early days of photoemission. Yet, the existence and nature of the Fe(001) surface state remain a subject of ongoing debate. Fe(001) is considered a prototypical transition metal system and moreover, one of the key players in the spintronics research. Here, we present the electronic structure of Fe(001) epitaxially grown on Au(001), mapped by high-resolution ARPES within the entire surface Brillouin zone, to demonstrate for the first time the exact location and extent of the Fe(001) surface state. The experimental results are supported by the relativistic slab calculations performed using density functional theory (DFT). The surface state observed for the pristine Fe(001) surface vanishes after overnight rest of the sample in ultrahigh vacuum as well as after intentional exposure to 5 Langmuir of oxygen which proves that it is not topologically protected. Furthermore, the dispersion of the surface state is found to depend on the relative orientation of the magnetization, which is explained based on the DFT results as related to the Rashba effect. These new experimental and theoretical results contribute to the existing knowledge on the electronic properties of Fe(001) with relevance for the basic research as well as for spintronic effects, such as tunneling anisotropic magnetoresistance.

We investigate the thermal reduction of TiO 2 in ultra-high vacuum. Contrary to what is usually assumed, we observe that the maximal surface reduction occurs not during the heating, but during the cooling of the sample back to room temperature. We describe the self-reduction, which occurs as a result of differences in the energies of defect formation in the bulk and surface regions. The findings presented are based on X-ray photoelectron spectroscopy carried out in - operando during the heating and cooling steps. The presented conclusions, concerning the course of redox processes, are especially important when considering oxides for resistive switching and neuromorphic applications and also when describing the mechanisms related to the basics of operation of solid oxide fuel cells.

Many properties of real materials can be modeled using ab initio methods within a single-particle picture. However, for an accurate theoretical treatment of excited states, it is necessary to describe electron-electron correlations including interactions with bosons: phonons, plasmons, or magnons. In this work, by comparing spin- and momentum-resolved photoemission spectroscopy measurements to many-body calculations carried out with a newly developed first-principles method, we show that a kink in the electronic band dispersion of a ferromagnetic material can occur at much deeper binding energies than expected ( E b  = 1.5 eV). We demonstrate that the observed spectral signature reflects the formation of a many-body state that includes a photohole bound to a coherent superposition of renormalized spin-flip excitations. The existence of such a many-body state sheds new light on the physics of the electron-magnon interaction which is essential in fields such as spintronics and Fe-based superconductivity. The conduction electron and magnon interactions are essential for the understanding and development of spintronics and superconductivity. Here the authors show a deep binding energy kink in spin-resolved photoemission spectra which is understood as a signature the many-body spin flip excitation in Fe single crystal thin film.

Reaching the van Hove singularity (VHS) in a material enables the emergence of exotic electronic and magnetic phases, such as superconductivity and the quantum anomalous Hall effect. This is demonstrated in cuprates, magic‐angle bilayer graphene, and more recently, monolayer graphene interfaced with alkali and rare earth elements. Here, the europium density at the graphene/rhenium interface is modulated to tune the electron doping level in monolayer graphene across the VHS point, forming either a dense or diluted europium phase. The dense phase enables flat bands at the Fermi level, while graphene remains decoupled from the Re(0001) substrate in both cases. The Dirac point is shifted over 1.5 eV below the Fermi level, and europium lifts the degeneracy of the Dirac cones: one branch hybridizes with Eu 4f states, the other retains Dirac‐like dispersion, as corroborated by density functional theory. X‐ray absorption spectroscopy reveals a mixed Eu(II)/Eu(III) valence state in the dense phase and the persistence of Eu magnetic response up to room temperature in both. The intercalated phases exhibit exceptional thermal stability, with the diluted phase stable up to 960 K. These results highlight the potential of rare‐earth‐doped graphene for engineering flat bands, tunable Dirac‐cone splitting, and robust interfacial magnetism. The modulation of europium density at the graphene/rhenium interface enables electron doping of monolayer graphene both beneath and beyond the van Hove singularity. The interfacial europium is ferromagnetic, with a transition from a mixed Eu(II)/Eu(III) valence in the dense phase to a pure Eu(II) state in the diluted phase. Strong Re‐Eu interaction ensures exceptional thermal stability and potential applications.