Study And Modulation Of The Physical Properties Of Group VA 2D Materials Arsenene And Bismuthene

Because of their exceptional electronic,optoelectronic,mechanical,and topological properties,2D materials would become promising candidates in emerging electronic,optoelectronic,and spintronic devices.Group VA 2D materials have attracted intense attention in condensed matter physics and material science fields in recent five years due to their large band gap,high mobility,excellent mechanical properties,and nontrivially topological character.On the basis of recent studies of 2D materials,this paper presents systematical investigation and discussion on Group VA 2D materials arsenene and bismuthene by using first-principles calculations.Focusing on the fundamental properties and possible modulating approaches,the important results are summarized as following:1.It has found that arsenene alloyed by the same group elements can induce indirectdirect transition.The alloyed arsenenes are transformed from indirect to direct band gap or from semiconductor to metal as exerting external strain.Doping and adsorbing 3d transition metal atoms can implement the local magnetic moment in arsenene and give rise to various electronic properties,such as half-metal,metal,semiconductor,spin bipolar semiconductor,spin unipolar semiconductor,and spin bipolar gapless semiconductor,ect.The electronic and magnetic properties of doped arsenene are tunable when the external strain and electric field are applied,which may enable arsenene more competitive in the practical applications.2.2D bismuthene single-layer is a topological insulator with novel Rashba effect.The electronic properties,topological character,and Rashba effect of bismuthene single-layer can be modulated by the external strain and electric field,showing abundant spintronic properties.Bismuthene double-layer is a topological semimetal and has interlayer coupling-and electric field-tunable band structure.When only the top-surface of bismuthene is oxidized,ie.,realizing sublattice half-oxidized bismuthene(SHO-Bi),it transforms into an inversion-asymmetry topological insulator with dramatic Rashba type spin-splitting.The electronic properties,topological character,and Rashba effect of SHOBi can be also modulated by applying external strain.In experiment,the h-BN is a suitable substrate for SHO-Bi.In asymmetrically functionalized bismuthene,the triggered sublattice potential coupling with the spin-orbit interaction gives rise to the unexpected spin-valley coupling effect.In particular,introducing Mo atom can further remove the spin-valley degeneracy,rendering valley polarization effect between K and K` points.This is helpful for the bismuthene applying to valley Hall devices in the future.3.Motivated by the realization of planar bismuthene grown on Si C substrate,we theoretically construct hydrogenated bismuthene(H-Bi)model to simulate the newly fabricated bismuthene.Through studying 22 kinds of adatoms adsorbed on H-Bi,it finds that some nonmagnetic atoms can perturb the intrinsic quantum spin Hall state of H-Bi owing to strong orbital hybridization effect.However,Group VA and VIA atoms produce new quantum spin Hall state even though the strong orbital hybridization also emerges between adatoms and Bi atoms.Surprisingly,4d and 5d transition-metal atoms can induce fascinating quantum anomalous Hall state.