Search

By obtaining the real magnetic anisotropy energy (MAE) under different strains, when 1.5% ε < 1.8%, due to spontaneous valley polarization, intrinsic out-of-plane (OOP) magnetic anisotropy, and a chiral edge state, the VQAHE can reliably appear between two HVM states.

A new two-dimensional metal-boride, namely, a NiB2 monolayer, is proposed to possess an anisotropic nodal loop state that is protected by nonsymmorphic glide mirror symmetry.

Two-dimensional (2D) nodal-loop semimetal (NLSM) materials have attracted much attention for their high-speed and low-consumption transporting properties as well as their fantastic symmetry protection mechanisms. In this paper, using systematic first-principles calculations, we present an excellent NLSM candidate, a 2D AlSb monolayer, in which the conduction and valence bands cross with each other forming fascinating multiple nodal-loop (NL) states. The NLSM properties of the AlSb monolayer are protected by its glide mirror symmetry, which was confirmed using a symmetry-constrained six-band tight-binding model. The transport properties of the AlSb monolayer under in-plane uniaxial strains are also studied, based on a non-equilibrium Green's function method. It is found that both compressive and tensile strains from -10% to 10% improve the transporting properties of AlSb, and it is interesting to see that flexure configurations are energetically favored when compressive uniaxial strains are applied. Our studies not only provide a novel 2D NLSM candidate with a new symmetry protection mechanism, but also raise the novel possibility for the detection of out-of-plane flexure in 2D semimetal materials.

Nodal-ring materials with a spin-polarized feature have attracted intensive interest recently due to their exotic properties and potential applications in spintronics. However, such a type of two-dimensional (2D) lattice is rather rare and difficult to realize experimentally. Here, we identify the first 2D Honeycomb-Kagome (HK) lattice, Mn-Cyanogen, as a new single-spin nodal-ring material by using first-principles calculations. Mn-Cyanogen shows gapless and semiconducting properties in spin-up and spin-down orientations, respectively, indicating a spin-gapless semiconductor nature. Remarkably, a spin-polarized nodal ring induced by px,y/pz band inversion is captured from the 3D band structure, which is irrelevant to spin-orbit coupling. The origin of the single-spin nodal-ring can be further clarified by the effective tight-binding (TB) model. These results open a new avenue to achieving spin-polarized nodal-ring materials with promising applications in spintronic devices.

A great obstacle for the practical applications of the quantum anomalous Hall (QAH) effect is the lack of suitable two-dimensional (2D) materials with a sizable nontrivial band gap, high Curie temperature, and high carrier mobility. Based on first-principles calculations, here, we propose the realizations of these intriguing properties in asymmetry-functionalized 2D SnHN and SnOH lattices. Spin-polarized band structures reveal that SnOH monolayer exhibits a spin gapless semiconductor (SGS) feature, whereas SnNH is converted to SGS under compressive strain. The Curie temperature of SnOH reaches 266 K, as predicted by Monte Carlo simulation, and it is comparable to the room temperature. When the spin and orbital degrees of freedom are allowed to couple, both systems become large-gap QAH insulators with fully spin-polarized half-metallic edge states and higher Fermi velocity of 4.9 × 105 m s-1. These results pave a new way for designing topological field transistors in group-IV honeycomb lattices.

One-dimensional (1D) nanowires (NWs) with robust half-metallicity are a rising star in spintronics. Herein, we theoretically investigate the magnetic and electronic properties of 3d transition-metal tribromide NWs, i.e. TMBr3 (TM = Sc, Ti, V, Cr, Co, and Cu). These systems represent repeated TMBr3 motifs with octahedral configuration, and are expected to be synthesized in a nanotube using an established method. Among these NWs, both VBr3 and CuBr3 NWs exhibit a ferromagnetic (FM) ground state, accompanied by sizable magnetocrystalline anisotropic energy, which is dominated by the superexchange coupling between the TM atoms. Strikingly, a half-metallic nature with a magnetic moment of 4.0μB per unit cell is predicted for the VBr3 NW. By combining with a tight-binding model, we demonstrate that the origin behind the half-metallicity is the half-filled e2 orbitals of the V atoms. The Curie temperature is evaluated to be up to 80 K using Monte Carlo simulations, which is comparable to the temperature of liquid nitrogen. We also find that the half-metallic behavior shows a favorable tolerance to the longitudinal elongation of the wire (∼10%). Additionally, a transition from FM semiconductor to half-metal can be realized in the CuBr3 NW through carrier doping. The coexistence of intrinsic high-temperature FM ordering and half-metallicity endows 1D TMBr3 NWs with great promise for spintronic and photoelectron device applications.