The attractive mechanical and electronic properties of freestanding graphene has led to the exploration of two-dimensional (2D) materials which can be integrated with contemporary electronics. As a 2D analog of graphene, stanene has become a hopeful candidate for 2D films due to its excellent quantum effects, superconductivity, and thermoelectric properties. Focusing on the promising 2D elemental material stanene, the fundamental electronic properties and experimental preparation of this material are reviewed. The prospects of utilizing the ability to manipulate the electronic properties of stanene for nanoelectronic and optoelectronic applications are determined.

The Dirac cone structure provides massless Fermions, ultrahigh carrier mobility, and many other novel features that are significant for massless and dissipationless quantum devices. The anisotropic Dirac cone has the advantage of anisotropic Fermi velocity and carrier mobility, which is different from the isotropic Dirac cone. Here we report two different configurations of B 2 Se monolayers with anisotropic Dirac cones. Fully optimized B 2 Se, as a rare two-dimensional pure planar pristine honeycomb structure, can maintain good structural integrity at higher temperatures up to 1000 K in ab initio molecular dynamics simulation, Young's modulus and Poisson's ratio show high anisotropy, the Fermi velocity of 10 6 m/s is the same order of magnitude as graphene. Moreover, we analyze the rationality of the existence of Dirac cones in the structure through wave functions and symmetry. This work provides novel candidates for finding direction-dependent, massless, and dissipationless quantum devices.

A large bulk band gap is critical for the application of two-dimensional topological insulators (TIs) in spintronic devices operating at room temperature. On the basis of first-principles calculations, we predict BiXH (X = OH, SH) monolayers as TIs with an extraordinarily large bulk gap of 820 meV for BiOH and 850 meV for BiSH, and propose a tight-binding model considering spin-orbit coupling to describe the electronic properties of BiXH. These large gaps are entirely due to the strong spin-orbit interaction related to the pxy orbitals of the Bi atoms of the honeycomb lattice. The orbital filtering mechanism can be used to understand the topological properties of BiXH. The XH groups simply remove one branch of orbitals (pz of Bi) and reduce the trivial 6-band lattice into a 4-band, which is topologically non-trivial. The topological characteristics of BiXH monolayers are confirmed by nonzero topological invariant Z2 and a single pair of gapless helical edge states in the bulk gap. Owing to these features, the BiXH monolayers of the large-gap TIs are an ideal platform to realize many exotic phenomena and fabricate new quantum devices working at room temperature.

Rashba spin−orbit coupling (SOC) in topological insulators (TIs) is a very interesting phenomenon and has received extensive attention in two-dimensional (2D) materials. However, the coexistence of Rashba SOC and band topology, especially for materials with a square lattice, is still lacking. Here, by using first-principles calculations, we propose for the first time a SeTe monolayer as a 2D candidate with these novel properties. We find that the square lattice exhibits anisotropic band dispersions near the Fermi level and a Rashba effect related to large SOC and inversion asymmetry, which leads to a Dirac semimetal state. Another prominent feature is that SeTe can achieve a topological state under a tensile strain of only 1%, characterized by the Z 2 invariant and helical edge states. Our findings demonstrate that SeTe is a promising material for novel electronic and spintronics applications.