The quantum spin Hall (QSH) effect is promising for achieving dissipationless transport devices due to their robust gapless edge states inside insulating bulk gap. However, the currently discussed QSH insulators usually suffer from ultrahigh vacuum or low temperature due to the small bulk gap, which limits their practical applications. Searching for large-gap QSH insulators is highly desirable. Here, the tunable QSH state of a Bi(110) films with a black phosphorus (BP) structure, which is robust against structural deformation and electric field, is explored by first-principles calculations. It is found that the two-monolayer BP-Bi(110) film obtains a tunable large bulk gap by strain engineering and its QSH effect shows a favorable robustness within a wide range of combinations of in-plane and out-of-plane strains, although a single in-plane compression or out-of-plane extension may restrict the topological phase due to the self-doping effect. More interestingly, in view of biaxial strain, two competing physics on band topology induced by bonding–antibonding and px,y–pz band inversions are obtained. Meanwhile, the QSH effect can be persevered under an electric field of up to 0.9 V/Å. Moreover, with appropriate in-plane strain engineering, a nontrivial topological phase in a four-monolayer BP-Bi(110) film is identified. Our findings suggest that these two-dimensional BP-Bi(110) films are ideal platforms of the QSH effect for low-power dissipation devices.Keywords: Bi(110) film; electric field; first-principles calculations; quantum spin Hall effect; strain engineering; topological insulator;

The development of multifunctional spintronic devices requires simultaneous control of multiple degrees of freedom of electrons, such as charge, spin and orbit, and especially a new physical functionality can be realized by combining two or more different physical mechanisms in one specific device. Here, we report the realization of novel tunneling rectification magnetoresistance (TRMR), where the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated in Co/CoO–ZnO/Co magnetic tunneling junctions with asymmetric tunneling barriers. Moreover, by simultaneously applying direct current and alternating current to the devices, the TRMR has been remarkably tuned in the range from −300% to 2200% at low temperature. This proof-of-concept investigation provides an unexplored avenue towards electrical and magnetic control of charge and spin, which may apply to other heterojunctions to give rise to more fascinating emergent functionalities for future spintronics applications.

•(FeCo)xGe1–x films with/without hydrogen are prepared by magnetron sputtering.•Magnetism is studied quantitatively by static and dynamic magnetization measurements.•Hydrogen enhances magnetization and exchange interaction in (FeCo)0.70Ge0.30-H films.•Enhanced exchange interaction mediated by both holes and H1s electrons is proposed.(FeCo)xGe1–x-H and (FeCo)xGe1–x films with high FeCo concentration were prepared by magnetron sputtering, and hydrogen enhanced magnetization and exchange interaction were found by static and dynamic magnetization measurements. The static magnetization measurements demonstrate that the saturation magnetization of (FeCo)0.70Ge0.30-H films is high up to 567 emu/cm3 at room temperature, which is about 170% higher than that of (FeCo)0.70Ge0.30 films. The dynamic magnetization measurements indicate that the exchange interaction in term of spin-wave stiffness constant D is 176.2 meV·Å2 in (FeCo)0.70Ge0.30-H films, which is about 156% larger than that in (FeCo)0.70Ge0.30 films. It is proposed that the hydrogen enhanced exchange interaction is mediated by both holes and H1s electrons in (FeCo)xGe1–x-H films. This may open an alternative way to design new spintronic materials by hydrogen enhancing magnetization and exchange interaction.

Electric-field control of magnetic and transport properties of magnetic tunnel junctions has promising applications in spintronics. Here, we experimentally demonstrate a reversible electrical manipulation of memristance, magnetoresistance, and exchange bias in Co/CoO–ZnO/Co magnetic tunnel junctions, which enables the realization of four nonvolatile resistance states. Moreover, greatly enhanced tunneling magnetoresistance of 68% was observed due to the enhanced spin polarization of the bottom Co/CoO interface. The ab initio calculations further indicate that the spin polarization of the Co/CoO interface is as high as 73% near the Fermi level and plenty of oxygen vacancies can induce metal–insulator transition of the CoO1−v layer. Thus, the electrical manipulation mechanism on the memristance, magnetoresistance and exchange bias can be attributed to the electric-field-driven migration of oxygen ions/vacancies between very thin CoO and ZnO layers.

Competitive adsorption of prototype molecules such as 12CO, 13CO and CO2 at the two typical fivefold coordinated Ti5c4+ cation sites of reduced rutile TiO2(110) surfaces was studied in a newly designed UHV-FTIR system. The measured binding energies of 12CO, 13CO or CO2 adsorbed at two kinds of Ti5c4+ sites are different. The molecular occupying probability at these sites depends on the binding energy of the adsorbed molecules; while, the molecular exchanging probability at these sites depends on their binding energy difference due to the presence of competitive adsorption. A simple thermodynamic equilibrium model was proposed to qualitatively interpret the adsorption and competitive adsorption mechanisms. These results will contribute to the elucidation of the (photo)catalytic process on TiO2(110) surfaces.

Opening up a band gap without lowering high carrier mobility and finding a suitable substrate material are a challenge for designing silicon-based nanodevices. Using density functional theory calculations incorporating vdW corrections, we find that the semiconducting silicane monolayer is free of dangling bonds, providing an ideal substrate for silicene to sit on. The nearly linear band dispersion character of silicene with a sizable band gap (44–61 meV) opening is obtained in all heterobilayers (HBLs). We also find that the effective masses of electrons and holes near the Dirac point (ranging from 0.033 to 0.045m0) are very small in HBLs, and thus high carrier mobility (105cm2 V–1 s–1) of silicene is expected. These characteristics of HBLs can be flexibly modulated by applying bias voltage or strain, suitable for the high-performance FET channel operating at room temperature.

A series of FeCoB–SiO2 granular films were deposited on Kapton flexible substrates by magnetron co-sputtering technique at room temperature. All films are amorphous with granular morphology. The coercivity in the easy axis (Hce) and the resistivity (ρ) decrease with the decrease of the Ar pressure, but they decrease with the increase of the film thickness. The granular films deposited at low Ar pressure exhibit obvious in-plane uniaxial magnetic anisotropy. Excellent soft magnetic properties with the Hce as low as 1.57 Oe was obtained in the 500 nm films deposited at 0.3 Pa. In addition, high ρ (∼3.5 mΩ cm), relatively high complex permeability (μ′ = 152.8 at low frequency and μmax″=221.2) and ferromagnetic resonance frequency (fr ∼ 3.61 GHz) were simultaneously obtained.

Competitive adsorption of prototype molecules such as 12CO, 13CO and CO2 at the two typical fivefold coordinated Ti5c4+ cation sites of reduced rutile TiO2(110) surfaces was studied in a newly designed UHV-FTIR system. The measured binding energies of 12CO, 13CO or CO2 adsorbed at two kinds of Ti5c4+ sites are different. The molecular occupying probability at these sites depends on the binding energy of the adsorbed molecules; while, the molecular exchanging probability at these sites depends on their binding energy difference due to the presence of competitive adsorption. A simple thermodynamic equilibrium model was proposed to qualitatively interpret the adsorption and competitive adsorption mechanisms. These results will contribute to the elucidation of the (photo)catalytic process on TiO2(110) surfaces.