Controllable orbital angular momentum monopoles in chiral topological semimetals.

The emerging field of orbitronics aims to generate and control orbital angular momentum for information processing. Chiral crystals are promising orbitronic materials because they have been predicted to host monopole-like orbital textures, where the orbital angular momentum aligns isotropically with the electron's crystal momentum. However, such monopoles have not yet been directly observed in chiral crystals.

Giant Topological Hall Effect and Colossal Magnetoresistance in Heusler Ferromagnet near Room Temperature.

Colossal magnetoresistance (CMR) is an exotic phenomenon that allows for the efficient magnetic control of electrical resistivity and has attracted significant attention in condensed matter due to its potential for memory and spintronic applications. Heusler alloys are the subject of considerable interest in this context due to the electronic properties that result from the nontrivial band topology. Here, the observation of CMR near room temperature is reported in the shape memory Heusler alloy NiMnIn, which is attributed to the combined effects of magnetic field-induced martensite twin variant reorientation (MFIR) and magnetic field-induced structural phase transformation (MFIPT).

Reducing crystal symmetry to generate out-of-plane Dzyaloshinskii-Moriya interaction.

The Dzyaloshinskii-Moriya antisymmetric exchange interaction (DMI) stabilises topological spin textures with promising future spintronics applications. According to crystal symmetry, the DMI can be categorized as four different types that favour different chiral textures. Unlike the other three extensively-investigated types, out-of-plane DMI, as the last type that favours in-plane chirality, remained missing so far.

Exciton-Exciton Interaction in Monolayer MoSe from Mutual Screening of Coulomb Binding.

Excitons in two-dimensional (2D) semiconductors are particularly exciting, as reduced screening and dimensional confinement foster their pronounced many-body interactions. Optical pumping is typically used to create excitons so as to study their properties, but at the same time such pumping can also create unbound charge carriers. This makes experimental determination of the exciton-exciton interactions difficult.

Long-range phase coherence and tunable second order -Josephson effect in a Dirac semimetal 1T-PtTe.

Superconducting diode effects have recently attracted much attention for their potential applications in superconducting logic circuits. Several pathways have been proposed to give rise to non-reciprocal critical currents in various superconductors and Josephson junctions. In this work, we establish the presence of a large Josephson diode effect in a type-II Dirac semimetal 1T-PtTe facilitated by its helical spin-momentum locking and distinguish it from extrinsic geometric effects.

Parallel Logic Operations in Electrically Tunable Two-Dimensional Homojunctions.

Two-dimensional materials show great potential for future electronics beyond silicon materials. Here, we report an exotic multiple-port device based on multiple electrically tunable planar p-n homojunctions formed in a two-dimensional (2D) ambipolar semiconductor, tungsten diselenide (WSe). In this device, we prepare multiple gates consisting of a global gate and several local gates, by which electrostatically induced holes and electrons are simultaneously accumulated in a WSe channel, and furthermore, at the boundaries, p-n junctions are formed as directly visualized by Kelvin probe force microscopy.

Multicore memristor from electrically readable nanoscopic racetracks.

The manipulation and detection of mobile domain walls in nanoscopic magnetic wires underlies the development of multibit memories. The studies of such domain walls have focused on macroscopic wires that allow for optical detection by using magneto-optic effects. In this study, we demonstrated the electrical tracking with a spatial resolution of better than 40 nm of multiple mobile domain walls in nanoscopic racetracks, using a set of anomalous Hall detectors integrated into the racetracks.

Initialization-Free and Magnetic Field-Free Spin-Orbit p-Bits with Backhopping-like Magnetization Switching for Probabilistic Applications.

Probabilistic bits (p-bits) with thermal- and spin torque-induced nondeterministic magnetization switching are promising candidates for performing probabilistic computing. Previously reported spin torque p-bits include volatile low-energy barrier nanomagnets (LBNMs) with spontaneously fluctuating magnetizations and initialization-necessary nonvolatile magnets. However, initialization-free nonvolatile spin torque p-bits are still lacking.

Computational elements based on coupled VO oscillators via tunable thermal triggering.

Computational technologies based on coupled oscillators are of great interest for energy efficient computing. A key to developing such technologies is the tunable control of the interaction among oscillators which today is accomplished by additional electronic components. Here we show that the synchronization of closely spaced vanadium dioxide (VO) oscillators can be controlled via a simple thermal triggering element that itself is formed from VO.

Defect-Free Nanowelding of Bilayer SnSe Nanoplates.

Nanowelding is a bottom-up technique to create custom-designed nanostructures and devices beyond the precision of lithographic methods. Here, a new technique is reported based on anisotropic lubricity at the van der Waals interface between monolayer and bilayer SnSe nanoplates and a graphene substrate to achieve precise control of the crystal orientation and the interface during the welding process. As-grown SnSe monolayer and bilayer nanoplates are commensurate with graphene's armchair direction but lack commensuration along graphene's zigzag direction, resulting in a reduced friction along that direction and a rail-like, 1D movement that permits joining nanoplates with high precision.

Terahertz Spin-Conductance Spectroscopy: Probing Coherent and Incoherent Ultrafast Spin Tunneling.

Thin-film stacks | consisting of a ferromagnetic-metal layer and a heavy-metal layer are spintronic model systems. Here, we present a method to measure the ultrabroadband spin conductance across a layer between and at terahertz frequencies, which are the natural frequencies of spin-transport dynamics. We apply our approach to MgO tunneling barriers with thickness = 0-6 Å.

Current-induced domain wall motion in a van der Waals ferromagnet FeGeTe.

The manipulation of spin textures by spin currents is of fundamental and technological interest. A particularly interesting system is the 2D van der Waals ferromagnet FeGeTe in which Néel-type skyrmions have recently been observed. The origin of these chiral spin textures is of considerable interest.

Dynamic Manipulation of Chiral Domain Wall Spacing for Advanced Spintronic Memory and Logic Devices.

Nanoscopic magnetic domain walls (DWs), via their absence or presence, enable highly interesting binary data bits. The current-controlled, high-speed, synchronous motion of sequences of chiral DWs in magnetic nanoconduits induced by current pulses makes possible high-performance spintronic memory and logic devices. The closer the spacing between neighboring DWs in an individual conduit or nanowire, the higher the data density of the device, but at the same time, the more difficult it is to read the bits.

All-Oxide Metasurfaces Formed by Synchronized Local Ionic Gating.

Ionic gating of oxide thin films has emerged as a novel way of manipulating the properties of thin films. Most studies are carried out on single devices with a three-terminal configuration, but, by exploring the electrokinetics during the ionic gating, such a configuration with initially insulating films leads to a highly non-uniform gating response of individual devices within large arrays of the devices. It is shown that such an issue can be circumvented by the formation of a uniform charge potential by the use of a thin conducting underlayer.

Weyl spin-momentum locking in a chiral topological semimetal.

Spin-orbit coupling in noncentrosymmetric crystals leads to spin-momentum locking - a directional relationship between an electron's spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin-momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin-momentum locking has remained elusive in experiments. Theory predicts that Weyl spin-momentum locking can only be realized in structurally chiral cubic crystals in the vicinity of Kramers-Weyl or multifold fermions.

A CuBHT-Graphene van der Waals Heterostructure with Strong Interlayer Coupling for Highly Efficient Photoinduced Charge Separation.

Two-dimensional van der Waals heterostructures (2D vdWhs) are of significant interest due to their intriguing physical properties critically defined by the constituent monolayers and their interlayer coupling. Synthetic access to 2D vdWhs based on chemically tunable monolayer organic 2D materials remains challenging. Herein, the fabrication of a novel organic-inorganic bilayer vdWh by combining π-conjugated 2D coordination polymer (2DCP, i.

Intrinsic supercurrent non-reciprocity coupled to the crystal structure of a van der Waals Josephson barrier.

Non-reciprocal electronic transport in a spatially homogeneous system arises from the simultaneous breaking of inversion and time-reversal symmetries. Superconducting and Josephson diodes, a key ingredient for future non-dissipative quantum devices, have recently been realized. Only a few examples of a vertical superconducting diode effect have been reported and its mechanism, especially whether intrinsic or extrinsic, remains elusive.

Thickness-Tunable Zoology of Magnetic Spin Textures Observed in FeGeTe.

The family of two-dimensional (2D) van der Waals (vdW) materials provides a playground for tuning structural and magnetic interactions to create a wide variety of spin textures. Of particular interest is the ferromagnetic compound FeGeTe that we show displays a range of complex spin textures as well as complex crystal structures. Here, using a high-brailliance laboratory X-ray source, we show that the majority (1 × 1) FeGeTe (FGT5) phase exhibits a structure that was previously considered as being centrosymmetric but rather lacks inversion symmetry.

Observation of the Fluctuation Spin Hall Effect in a Low-Resistivity Antiferromagnet.

The spin Hall effect (SHE) can generate a pure spin current by an electric current, which is promisingly used to electrically control magnetization. To reduce the power consumption of this control, a giant spin Hall angle (SHA) in the SHE is desired in low-resistivity systems for practical applications. Here, critical spin fluctuation near the antiferromagnetic (AFM) phase transition in chromium (Cr) is proven to be an effective mechanism for creating an additional part of the SHE, named the fluctuation spin Hall effect.

Generation of out-of-plane polarized spin current by spin swapping.

The generation of spin currents and their application to the manipulation of magnetic states is fundamental to spintronics. Of particular interest are chiral antiferromagnets that exhibit properties typical of ferromagnetic materials even though they have negligible magnetization. Here, we report the generation of a robust spin current with both in-plane and out-of-plane spin polarization in epitaxial thin films of the chiral antiferromagnet MnSn in proximity to permalloy thin layers.

Li iontronics in single-crystalline T-NbO thin films with vertical ionic transport channels.

The niobium oxide polymorph T-NbO has been extensively investigated in its bulk form especially for applications in fast-charging batteries and electrochemical (pseudo)capacitors. Its crystal structure, which has two-dimensional (2D) layers with very low steric hindrance, allows for fast Li-ion migration. However, since its discovery in 1941, the growth of single-crystalline thin films and its electronic applications have not yet been realized, probably due to its large orthorhombic unit cell along with the existence of many polymorphs.

Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, KVSb.

Materials with Kagome nets are of particular importance for their potential combination of strong correlation, exotic magnetism, and electronic topology. KVSb was discovered to be a layered topological metal with a Kagome net of vanadium. Here, we fabricated Josephson Junctions of KVSb and induced superconductivity over long junction lengths.

Chiral antiferromagnetic Josephson junctions as spin-triplet supercurrent spin valves and d.c. SQUIDs.

Spin-triplet supercurrent spin valves are of practical importance for the realization of superconducting spintronic logic circuits. In ferromagnetic Josephson junctions, the magnetic-field-controlled non-collinearity between the spin-mixer and spin-rotator magnetizations switches the spin-polarized triplet supercurrents on and off. Here we report an antiferromagnetic equivalent of such spin-triplet supercurrent spin valves in chiral antiferromagnetic Josephson junctions as well as a direct-current superconducting quantum interference device.