The Oretical Study On The Novel Quantum States Of Functionalized V-V A Binary Single-layer Spin Valley Coupling

In solid materials,the band theory tells us that there are conductive metals and non-conductive insulators.With the help of topological classification of closed surfaces in mathematics,insulators can be subdivided into ordinary insulators and topological non-mediocre insulators?e.g.,3D topological insulators,quantum spin hall insulators,quantum anomalous hall insulators,etc.?by introducing topological invariants of electronic energy bands in momentum space.Similarly,metal states can be divided into ordinary and topological metals.In fact,the discovery of these novel quantum states,the observation and application exploration of the theoretical prediction and experimental synthesis of physical properties of real materials,and the study of topological phase transitions between different quantum states have become hot topics in condensed matter physics.Based on two-dimensional V-V experimental synthesis of layered materials and theoretical prediction,based on first principles calculation and tight-binding approximation,simulation based on the functional binary V-V single compounds found in the two kinds of novel quantum state,respectively topological spin-valley of coupling insulators and spin coupling of Dirac semimetal concrete research contents and results are as follows:?1?The existing 2D topological insulators are mostly symmetrical structures with the body spin degenerate,so it is impossible to realize the comprehensive application of topological boundary state,body spin and energy valley.Based on the first-principles calculation and the tight-bound Wannier function method,we found a novel topological state topological spin valley coupling insulator with both spin and valley polarization in a two-dimensional fluorinated BiSb monolayer.The results show that BiSbF₂ monolayer has the same coupling spin-valley polarization as MoS₂nanometer monolayer,and has many excellent properties:?i?The large spin-splitting energy—conduction band has a spin-splitting energy of up to 491meV;?ii?Carrier mobility of electron and hole were 22500 cm²V^-1s^-11 and 4370 cm²V^-1s^-1;?iii?The phase energy gap can be linearly regulated by strain.In addition,through the band inversion analysis,surface state and topology and Z₂ topological invariants of the calculation,we found that BiSbF₂ for typical broadband gap of 2D topological insulators BiSbF₂ these peculiar properties can be able to keep the topology in BN substrate spin-valley coupling of the insulation material for spin valley electronics and topology may integration and application of physics.?2?The 2D Dirac material will open the energy gap under the effect of spin orbit coupling?SOC?,so it is essentially a quantum spin hall insulator,or 2D topological insulator.In this paper,by applying strain to the functionalized SbAs monolayer[SbAsX₂?X=H,F,Cl,Br,I?],it was found that SbAsH₂ had the spin valley polarization Dirac state induced by SOC under the tensile strain of 2.3%,that is,spin valley coupling Dirac semi-metal.Because the symmetry of center inversion is broken,the linear Dirac energy band has spin splitting,and different Dirac energy valleys have opposite directions of spin magnetic moment and berry curvature.Single-layer film 2.3-SbAsH₂ not only has a large spin splitting energy??35?_e=421 meV and?35?_h=189 meV?,but also presents a large Fermi velocity??_F=8.79×10⁵m/s?.The analysis of topological properties shows that the singular quantum state is an intermediate state between ordinary insulator and topological insulator.The realization of this novel quantum state will provide a new way for the development of ultra-high speed and ultra-low-energy quantum transmission and an ideal platform for the development of Dirac spin valley electronics.