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Abstract Magnetization in a ferromagnetic layer could be manipulated by the spin-orbit torque whose generation commonly relies on the spin-orbit coupling from the adjacent heavy-metal layer within the bilayer. The fact that the magnetic topological insulator possesses both the ferromagnetic order with perpendicular anisotropy and inherent spin-orbit coupling inspires to realize such a torque-induced magnetization switching without forming any heterostructure with other materials. Here, only using a single layer of magnetically-doped topological insulator Cr:(Bi,Sb)2Te3, we realize a magnetization switching only by applying a large dc current. Assisted by the magnetic history, such a switching behaves nonvolatile under zero field but becomes volatile otherwise, as consistently shown by magnetoelectric transports and magneto-optical Kerr effect measurements. Static and quasistatic current are found to be equivalent for the switching. We propose that this switching may associate with the torque resulted from the spin-orbit coupling and the compositional asymmetry in the Cr-profile of the single layer.

Abstract The quasi-1D chiral edge states in a quantum anomalous Hall insulator are dissipationless, while the 2D helical surface states in a topological insulator are insensitive to spin-independent scatterings due to the topological protection. Both serve as essential ingredients for topological electronics. Here, we integrate these states into a single device using selective area epitaxy based on the molecular beam epitaxy technique. The chiral edge state comes from the quantum anomalous Hall insulator Cr:(Bi,Sb)2Te3, while the helical surface state comes from the intrinsic topological insulator (Bi,Sb)2Te3 which only interfaces with a partial edge of the former, forming a selective-area heterostructure. At the heterointerface, the chiral state in Cr:(Bi,Sb)2Te3 is allowed to be scattered into (Bi,Sb)2Te3 so that the incoming current will be redistributed according to the coordination between the chirality and helicity. Our device enables the collaboration between chiral and helical states for low-dissipative transport with tunable current dimension.

The Berezinskii-Kosterlitz-Thouless topological phase transition has been observed in various systems, and involves vortex-antivortex pairs binding/un-binding. Here, such a transition is observed in a 2D ferromagnetic quantum anomalous Hall insulator film, revealed by temperature-dependent magneto-electrical transport measurements.

The percolation plays an essential role in the physics of plateau transition, localization, and breakdown in quantum Hall (QH) systems. In practice, it always exists probably due to sample imperfections and has to be addressed before realizing the full potentials of topological electronics and qubits. Here, we investigate the cause, distribution, and number of the percolation in a quantum anomalous Hall (QAH) insulator of an anti-Hall bar geometry with two perimeters, which allows for probing both the inter- and intra-perimeter percolations by injecting currents into either or both perimeters. We discover the dual-QAH effect with opposite chiralities from these two perimeters, which exhibits linear modulations by the currents applied to both perimeters. By solving the formulation of such modulations with the Landauer–Büttiker formalism, the distribution and number of the inter-perimeter percolative channels could be identified. Strikingly, a dissipative constituent is detected in the transport of the QAH state, as revealed by the linear scalings in longitudinal conductivities versus the sum of currents injected to both perimeters, similar to that in the trivial-insulating state. Such a behavior unveils the quasi-2D nature of the intra-perimeter percolation, which superimposes onto and perturbs the dissipationless chiral edge transport. The formation of percolations is ascribed to the joint effect of the electric field, finite conductivity, and sample imperfections.

The Chern insulator manifests itself via the surface quantized Hall current and magnetoelectric effect. The manipulation of surface magnetizations enables a control of the dissipationless chiral transport and thus allows for potential applications of topological magnetoelectric devices with low-energy consumption. Here, we present experimental studies of bias-modulated switching the magnetic states utilizing the magnetoelectric coupling in a Chern insulator. This is achieved via applying a d.c. bias across the source and drain at various magnetic states, during which an effective magnetic field is developed to switch the quantum anomalous Hall state towards its opposite. Comprehensive transport studies show that the switch efficiency is proportional to the amplitude and applying time of the bias, depends on the initial magnetic state, but is insensitive to the electric polarity. Our results provide an efficient scheme to manipulate the Chern insulator and understanding on the electric breakdown of chiral edge states.

The spin-orbit torque (SOT) induced magnetic switching makes metal/magnetic insulators bilayers preferred in the energy efficient spintronic applications. Here the authors show SOT switching in W/TmIG bilayers and reveal the dimension crossover of SOT as a function of TmIG thickness.

Spin-polarized carriers could show an extra Hall component when moving through certain real-space topological spin textures. Here, He et al. report an exchange bias experienced by the topological spin textures living at the interface between a topological insulator and an adjacent antiferromagnet, suggesting a chiral spin texture is induced.

With the recent discovery of the quantum anomalous Hall insulator (QAHI), which exhibits the conductive quantum Hall edge states without external magnetic field, it becomes possible to create a topological superconductor (SC) by introducing superconductivity into these edge states. In this case, 2 distinct topological superconducting phases with 1 or 2 chiral Majorana edge modes were theoretically predicted, characterized by Chern numbers (N) of 1 and 2, respectively. We present spectroscopic evidence from Andreev reflection experiments for the presence of chiral Majorana modes in an Nb/(Cr0.12Bi0.26Sb0.62)2Te3 heterostructure with distinct signatures attributed to 2 different topological superconducting phases. The results are in qualitatively good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

We study the magnetic properties of W/Co40Fe40B20 (CoFeB)/MgO films using the spin-torque ferromagnetic resonance (ST-FMR) technique. This study takes the advantage of the spin Hall magnetoresistance (SMR) for generating an oscillating resistance, which is one of the necessary requirements for obtaining mixing voltage in the ST-FMR technique. We have measured both the as-grown and the annealed samples with different CoFeB layer thicknesses, which include the in-plane and out-of-plane magnetic anisotropies. The spectra for these two types of anisotropies show distinct signatures. By analyzing the ST-FMR spectra, we extract the effective anisotropy field for both types of samples. In addition, we investigate the influence of CoFeB thickness and annealing on the Gilbert damping constant. Our experiments show that by taking advantage of SMR, the ST-FMR measurement acts as an effective tool with high sensitivity for studying the magnetic properties of ultrathin magnetic films. [ABSTRACT FROM AUTHOR]

CaS, with a direct bandgap of 5.38 eV, is expected to be a strong candidate as the active-layer of high performance solar-blind UV photodiodes that have important applications in both civilian and military sectors. Here, we report that a seed-layer-assisted growth approach via molecular beam epitaxy can result in high crystalline quality rocksalt CaS thin films on zincblende GaAs substrates. The Au/CaS/GaAs solar-blind photodiodes demonstrated, more than five orders in its visible rejection power, a photoresponse of 36.8mA/w at zero bias and a corresponding quantum efficiency as high as 19% at 235 nm. [ABSTRACT FROM AUTHOR]

We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure. The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation. The surface reactivity of the adsorbed tellurium on this heterostructure is also intensified possibly benefitted from the effective transfer of the bath electrons. A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lyingd-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates [ABSTRACT FROM AUTHOR]

Magnetism in topological insulators (TIs) opens a topologically nontrivial exchange band gap, providing an exciting platform for manipulating the topological order through an external magnetic field. Here, we show that the surface of an antiferromagnetic thin film can magnetize the top and the bottom TI surface states through interfacial couplings. During the magnetization reversal, intermediate spin configurations are ascribed from unsynchronized magnetic switchings. This unsynchronized switching develops antisymmetric magnetoresistance spikes during magnetization reversals, which might originate from a series of topological transitions. With the high Néel ordering temperature provided by the antiferromagnetic layers, the signature of the induced topological transition persists up to ~90 K. [ABSTRACT FROM AUTHOR]

We have developed an incandescent Mo source to fabricate large-area single-crystalline MoSe2 thin films. The as-grown MoSe2 thin films were characterized using transmission electron microscopy, energy dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy, photoluminescence (PL), reflection high energy electron diffraction (RHEED) and angular resolved photoemission spectroscopy (ARPES). A new Raman characteristic peak at 1591 cm−1 was identified. Results from Raman spectroscopy, PL, RHEED and ARPES studies consistently reveal that large-area single crystalline mono-layer of MoSe2 could be achieved by this technique. This technique enjoys several advantages over conventional approaches and could be extended to the growth of other two-dimensional layered materials containing a low-vapor-pressure element. [ABSTRACT FROM AUTHOR]

The article offers information about the findings that provide important insights into the search for high-temperature quantum anomalous Hall insulator and other topologically related phenomena. It discusses the study the temperature limiting factors of the effect in Cr-doped (BiSb) 2Te3 systems using both transport and magneto-optical methods.

The combination of magnetism and topology in magnetic topological insulators (MTIs) has led to unprecedented advancements of time reversal symmetry-breaking topological quantum physics in the past decade. Compared with the uniform films, the MTI heterostructures provide a better framework to manipulate the spin-orbit coupling and magnetic/spin properties. In this review, we summarize the fundamental mechanisms related to the physical orders host in (Bi,Sb)2(Te,Se)3-based hybrid systems. Besides, we provide an assessment on the general strategies to enhance the magnetic coupling and spin-orbit torque strength through different structural engineering approaches and effective interfacial interactions. Finally, we offer an outlook of MTI heterostructures-based spintronics applications, particularly in view of their feasibility to achieve room-temperature operation.

The article offers information on the termination switching of antiferromagnetic proximity effect in topological insulator. It mentions the quantum anomalous Hall effect (QAHE) in magnetic topological insulators. It reports the ferromagnetism of topological insulator, with a Curie temperature induced by magnetic proximity effect (MPE) of an antiferromagnetic chromium selenide (CrSe).

Hydrogen sulfide (H2S) has long been considered as a toxic gas, but as research progressed, the idea has been updated and it has now been shown to have potent protective effects at reasonable concentrations. H2S is an endogenous gas signaling molecule in mammals and is produced by specific enzymes in different cell types. An increasing number of studies indicate that H2S plays an important role in cardiovascular homeostasis, and in most cases, H2S has been reported to be downregulated in cardiovascular diseases (CVDs). Similarly, in preclinical studies, H2S has been shown to prevent CVDs and improve heart function after heart failure. Recently, many H2S donors have been synthesized and tested in cellular and animal models. Moreover, numerous molecular mechanisms have been proposed to demonstrate the effects of these donors. In this review, we will provide an update on the role of H2S in cardiovascular activities and its involvement in pathological states, with a special focus on the roles of exogenous H2S in cardiac protection.