Manipulating Magnetic Damping of Fe/GeTe Heterostructures by Band Engineering.

Understanding and manipulating magnetic damping, particularly in magnetic heterostructures, is crucial for fundamental research, versatile engineering, and optimization. Although magnetic damping can be enhanced by the band hybridization between ferromagnetic and nonmagnetic materials at the interface, the contribution of individual subbands on the hybridized bands to magnetic damping is fully unexplored. Here, it is found that magnetic damping α is modified by the Fermi level in Fe/GeTe heterostructures via Bi doping.

Observation of In-Gap States in a Two-Dimensional CrI/NbSe Heterostructure.

Low-dimensional magnetic structures coupled with superconductors are promising platforms for realizing Majorana zero modes, which have potential applications in topological quantum computing. Here, we report a two-dimensional (2D) magnetic-superconducting heterostructure consisting of single-layer chromium diiodide (CrI) on a niobium diselenide (NbSe) superconductor. Single-layer CrI nanosheets, which hold antiferromagnetic (AFM) ground states by our first-principles calculations, were epitaxially grown on the layered NbSe substrate.

Switching Intrinsic Magnetic Skyrmions with Controllable Magnetic Anisotropy in van der Waals Multiferroic Heterostructures.

Magnetic skyrmions, topologically nontrivial whirling spin textures at nanometer scales, have emerged as potential information carriers for spintronic devices. The ability to efficiently create and erase magnetic skyrmions is vital yet challenging for such applications. Based on first-principles studies, we find that switching between intrinsic magnetic skyrmion and high-temperature ferromagnetic states can be achieved in the two-dimensional van der Waals (vdW) multiferroic heterostructure CrSeI/InTe by reversing the ferroelectric polarization of InTe.

The discovery of three-dimensional Van Hove singularity.

Arising from the extreme/saddle point in electronic bands, Van Hove singularity (VHS) manifests divergent density of states (DOS) and induces various new states of matter such as unconventional superconductivity. VHS is believed to exist in one and two dimensions, but rarely found in three dimension (3D). Here, we report the discovery of 3D VHS in a topological magnet EuCdAs by magneto-infrared spectroscopy.

Tunable quantum anomalous Hall effects in ferromagnetic van der Waals heterostructures.

The quantum anomalous Hall effect (QAHE) has unique advantages in topotronic applications, but it is still challenging to realize the QAHE with tunable magnetic and topological properties for building functional devices. Through systematic first-principles calculations, we predict that the in-plane magnetization induced QAHE with Chern numbers  = ±1 and the out-of-plane magnetization induced QAHE with high Chern numbers  = ±3 can be realized in a single material candidate, which is composed of van der Waals (vdW) coupled Bi and MnBiTe monolayers. The switching between different phases of QAHE can be controlled in multiple ways, such as applying strain or (weak) magnetic field or twisting the vdW materials.

Anisotropic Nonlocal Damping in Ferromagnet/α-GeTe Bilayers Enabled by Splitting Energy Bands.

The understanding and manipulation of anisotropic Gilbert damping is crucial for both fundamental research and versatile engineering and optimization. Although several works on anisotropic damping have been reported, no direct relationship between the band structure and anisotropic damping was established. Here, we observed an anisotropic damping in Fe/GeTe manipulated by the symmetric band structures of GeTe via angle-resolved photoemission spectroscopy.

Epitaxial growth and electronic properties of an antiferromagnetic semiconducting VI monolayer.

The van der Waals materials down to the monolayer (ML) limit provide a fertile platform for exploring low-dimensional magnetism and developing the novel applications of spintronics. Among them, due to the absence of the net magnetic moment, antiferromagnetic (AFM) materials have received much less attention than ferromagnetic ones. Here, by combining scanning tunneling microscopy and state-of-the-art first-principles calculations, we investigate the preparation, and electronic and magnetic properties of a vanadium(II) iodide (VI) ML.

Toward Room-Temperature Electrical Control of Magnetic Order in Multiferroic van der Waals Materials.

Electrical control of magnetic order in van der Waals (vdW) two-dimensional (2D) systems is appealing for high-efficiency and low-dissipation nanospintronic devices. For realistic applications, a vdW 2D material with ferromagnetic (FM) and ferroelectric (FE) orders coexisting and strongly coupling at room temperature is urgently needed. Here we present a potential candidate for nonvolatile electric-field control of magnetic orders at room temperature.

The role of primary physician training in improving regional standardized management of diabetes: a pre-post intervention study.

Background: Hierarchical diagnosis and treatment has been gradually implemented throughout the China. Primary physicians are the main force in primary-level medical and health services, which means that standardized training of primary-level doctors is indispensable.

Objectives: Evaluation of the effect of primary physician training on standardized management of diabetes, and comparison of the effects of different training models.

Tuning the interfacial spin-orbit coupling with ferroelectricity.

Detection and manipulation of spin current lie in the core of spintronics. Here we report an active control of a net spin Hall angle, θ(net), in Pt at an interface with a ferroelectric material PZT (PbZrTiO), using its ferroelectric polarization. The spin Hall angle in the ultra-thin Pt layer is measured using the inverse spin Hall effect with a pulsed tunneling current from a ferromagnetic LaSrMnO electrode.

MoB: a new multifunctional transition metal diboride monolayer.

Several layered transition metal borides can now be realized by a simple and general fabrication method (Fokwa et al 2018 Adv. Mater. 30 1704181), inspiring our interest to transition metal borides monolayer.

Real-space charge-density imaging with sub-ångström resolution by four-dimensional electron microscopy.

The distribution of charge density in materials dictates their chemical bonding, electronic transport, and optical and mechanical properties. Indirectly measuring the charge density of bulk materials is possible through X-ray or electron diffraction techniques by fitting their structure factors, but only if the sample is perfectly homogeneous within the area illuminated by the beam. Meanwhile, scanning tunnelling microscopy and atomic force microscopy enable us to see chemical bonds, but only on the surface.

Magnetizing topological surface states of BiSe with a CrI monolayer.

To magnetize surfaces of topological insulators without damaging their topological feature is a crucial step for the realization of the quantum anomalous Hall effect (QAHE) and remains as a challenging task. Through density functional calculations, we found that adsorption of a semiconducting two-dimensional van der Waals (2D-vdW) ferromagnetic CrI monolayer can create a sizable spin splitting at the Dirac point of the topological surface states of BiSe films. Furthermore, general rules that connect different quantum and topological parameters are established through model analyses.

Multifunctional 2D CuSe monolayer nanodevice.

In a very recent experimental work (Gao et al 2018 Adv. Mater. 30 1707055), a graphene-like CuSe monolayer (ML) was realized.

Axion Insulator State in a Ferromagnet/Topological Insulator/Antiferromagnet Heterostructure.

We propose the use of ferromagnetic insulator MnBiSe/BiSe/antiferromagnetic insulator MnBiSe heterostructures for the realization of the axion insulator state. Importantly, the axion insulator state in such heterostructures only depends on the magnetization of the ferromagnetic insulator and, hence, can be observed in a wide range of external magnetic fields. Using density functional calculations and model Hamiltonian simulations, we find that the top and bottom surfaces have opposite half-quantum Hall conductances, [Formula: see text] and [Formula: see text], with a sizable global spin gap of 5.

Probing Magnetism in Insulating CrGeTe by Induced Anomalous Hall Effect in Pt.

Two-dimensional ferromagnet CrGeTe (CGT) is so resistive below its Curie temperature that probing its magnetism by electrical transport becomes extremely difficult. By forming heterostructures with Pt, however, we observe clear anomalous Hall effect (AHE) in 5 nm thick Pt deposited on thin (<50 nm) exfoliated flakes of CGT. The AHE hysteresis loops persist to ∼60 K, which matches well to the Curie temperature of CGT obtained from the bulk magnetization measurements.

Negative differential conductance effect and electrical anisotropy of 2D ZrB monolayers.

Two-dimensional (2D) metal-diboride ZrB monolayers was predicted theoretically as a stable new electronic material (Lopez-Bezanilla 2018 Phys. Rev. Mater.

Direct in Situ Observation and Analysis of the Formation of Palladium Nanocrystals with High-Index Facets.

Synthesizing concave-structured nanoparticles (NP) with high-index surfaces offers a viable method to significantly enhance the catalytic activity of NPs. Current approaches for fabricating concave NPs, however, are limited. Exploring novel synthesis methods requires a thorough understanding of the competing mechanisms that contribute to the evolution of surface structures during NP growth.

How does the electric current propagate through fully-hydrogenated borophene?

We study the electronic transport properties of two-dimensional (2D) fully-hydrogenated borophene (namely, borophane), using density functional theory and non-equilibrium Green's function approaches. Borophane shows a perfect electrical transport anisotropy and is promising for applications. Along the peak- or equivalently the valley-parallel direction, 2D borophane exhibits a metallic characteristic and its current-voltage (I-V) curve shows a linear behavior, corresponding to the ON state in borophane-based nano-switches.

Revealing Surface Elemental Composition and Dynamic Processes Involved in Facet-Dependent Oxidation of PtCo Nanoparticles via in Situ Transmission Electron Microscopy.

Since catalytic performance of platinum-metal (Pt-M) nanoparticles is primarily determined by the chemical and structural configurations of the outermost atomic layers, detailed knowledge of the distribution of Pt and M surface atoms is crucial for the design of Pt-M electrocatalysts with optimum activity. Further, an understanding of how the surface composition and structure of electrocatalysts may be controlled by external means is useful for their efficient production. Here, we report our study of surface composition and the dynamics involved in facet-dependent oxidation of equilibrium-shaped PtCo nanoparticles in an initially disordered state via in situ transmission electron microscopy and density functional calculations.

Orbital Delocalization and Enhancement of Magnetic Interactions in Perovskite Oxyhydrides.

Recent experiments showed that some perovskite oxyhydrides have surprisingly high magnetic-transition temperature. In order to unveil the origin of this interesting phenomenon, we investigate the magnetism in SrCrO2H and SrVO2H on the basis of first-principles calculations and Monte Carlo simulations. Our work indicates that the Cr-O-Cr superexchange interaction in SrCrO2H is unexpectedly strong.