Research On Spin Hall Effect Of Light And Its Sensing Application In Weyl Semimetals

The spin Hall effect of light(SHEL)refers to the spin-dependent splitting induced by the refractive index gradient in the direction perpendicular to the incident plane,when the beam passes through an inhomogeneous medium.The SHEL has become a hot issue since its introduction and provided potential applications in fields of precision measurement,optical sensing and quantum information.However,the spin-dependent shift of SHEL in traditional interfaces is generally weak and greatly limits its development and application.Weyl semimetal(WSM)is a novel topological material taken Weyl fermion as quasi-particle,known as“three-dimensional graphene”.It comes with excellent electrical and optical properties,and has the potential to improve the regulation ability of SHEL and expand SHEL's application range.In this thesis,aiming at the weakness of SHEL in traditional interfaces,the studies of SHEL in WSMs are discussed systematically,and the influences and regulatory roles of WSMs' configuration parameters on SHEL are explored.On these bases,the weak signal enhancement technique,known as quantum weak measurement,is introduced to find the methods of sensing WSMs' configuration parameters and discriminating WSMs' type.Also,these works are extended to the research of other beam shifts.The specific results are summarized as follows:Firstly,a scheme of sensing the lattice spacing of type-I WSMs based on SHEL is proposed with the help of weak measurement.It is revealed that in ideal undoped type-I WSMs,the lattice spacing plays as essential a role as the Weyl points separation in the influences on SHEL,and the SHEL can be efficiently enhanced by adjusting the lattice spacing.After introducing the weak measurement technique,the SHEL shifts are amplified and measured in desirable accuracies,which show a one-to-one correspondence with the lattice spacing.Subsequently,a scheme of precisely sensing the lattice-spacing is proposed based on the amplified SHEL shifts.Secondly,a scheme of discriminating the type of WSMs based on the weak measurement of SHEL is proposed.It is found that in the case of small doping,the SHEL shifts in type-I WSMs almost show no dependence on Weyl cone's tilt degree,while the one in type-II WSMs are extremely sensitive to the variation of tilt degree.Using the weak measurement method,the tilt-dependent characteristics of amplified SHEL shifts in type-I and type-II WSMs appear more significant differences,so that the fast discrimination of WSMs' type can be realized.Meanwhile,this scheme can also be used to realize the precise sensing of Weyl cone's tilt degree,and the sensing sensitivity can reach up to 1461.55?m per tilt degree.Thirdly,a model of the Imbert-Fedorov(IF)and Goos-H(?)nchen(GH)effects associated with the SHEL in both type-I and type-II WSMs are established,where the roles of Weyl cone tilting and chemical doping on IF and GH shifts are discussed.It is revealed that the IF and GH shifts all show quasi-symmetry trends with the change of Weyl cone's tilt degree,which is mainly attributed to the dependence of WSMs' optical conductivities on the tilt degree.Meanwhile,the transition zone between type-I WSMs and type-II WSMs characterized by the tilt-dependent beam shifts,can be effectively reduced by adjusting chemical doping,so that the boundary between the two types of WSMs is further clarified.These findings may provide new theoretical supports for using IF or GH shifts as the probe to discriminate the type of WSMs,and to sense related configuration parameters of WSMs.