We theoretically investigate the reflected spatial Imbert–Fedorov(IF)shift of transverse-electric(TE)-polarized beam illuminating on a bulk Weyl semimetal(WSM).The spatial IF shift is enhanced significantly at two di...We theoretically investigate the reflected spatial Imbert–Fedorov(IF)shift of transverse-electric(TE)-polarized beam illuminating on a bulk Weyl semimetal(WSM).The spatial IF shift is enhanced significantly at two different frequencies close to the epsilon-near-zero(ENZ)frequency,where large values of reflection coefficients|r_(pp)|/|r_(ss)|are obtained due to the ENZ response induced different rapid increasing trends of|r_(pp)|and|r_(ss)|.Particularly,the tunable ENZ effect with tilt degree of Weyl cones and Fermi energy enables the enhanced spatial IF shift at different frequencies.The enhanced spatial IF shift also shows the adjustability of WSM thickness,incident angle and Weyl node separation.Our findings provide easy and available methods to enlarge and adjust the reflected IF shift of TE-polarized light with a WSM.展开更多
We establish the beam models of Goos–H?nchen(GH)and Imbert–Fedorov(IF)effects in tilted Weyl semimetals(WSMs),and systematically study the influences of Weyl cone tilting and chemical potential on the GH and IF shif...We establish the beam models of Goos–H?nchen(GH)and Imbert–Fedorov(IF)effects in tilted Weyl semimetals(WSMs),and systematically study the influences of Weyl cone tilting and chemical potential on the GH and IF shifts at a certain photon energy 1.96 eV.It is found that the GH and IF shifts in tilted type-Ⅰand type-ⅡWSMs are both almost symmetric about the Weyl cone tilting.Meanwhile,the GH and IF shifts in type-I WSMs almost do not change with the tilt degree of Weyl cones,while those in type-ⅡWSMs are extremely dependent on tilt degree.These trends are mainly due to the nearly symmetric distribution of WSMs conductivities,where the conductivities keep stable in type-I WSMs and gradually decrease with tilt degree in type-II WSMs.By adjusting the chemical potential,the boundary between type-I and type-II WSMs widens,and the dependence of the beam shifts on the tilt degree can be manipulated.Furthermore,by extending the relevant discussions to a wider frequency band,the peak fluctuation of GH shifts and the decrease of IF shifts occur gradually as the frequency increases,and the performance of beam shifts at photon energy 1.96 eV is equally suitable for other photon frequencies.The above findings provide a new reference for revisiting the beam shifts in tilted WSMs and determining the types of WSMs.展开更多
In this paper, we consider the electromagnetic scattering from periodic chiral structures. The structure is periodic in one direction and invariant in another direction. The electromagnetic fields in the chiral medium...In this paper, we consider the electromagnetic scattering from periodic chiral structures. The structure is periodic in one direction and invariant in another direction. The electromagnetic fields in the chiral medium are governed by the Maxwell equations together with the Drude-Born-Fedorov equations. We simplify the problem to a two-dimensional scattering problem and we show that for all but possibly a discrete set of wave numbers, there is a unique quasi-periodic weak solution to the diffraction problem. The diffraction problem can be solved by finite element method. We also establish uniform error estimates for the finite element method and the error estimates when the truncation of the nonlocal transparent boundary operators takes place.展开更多
In this paper, we consider the electromagnetic scattering by a periodic chiral structure. The media is homogeneous and the structure is periodic in one direction and invariant in another direction. The electromagnetic...In this paper, we consider the electromagnetic scattering by a periodic chiral structure. The media is homogeneous and the structure is periodic in one direction and invariant in another direction. The electromagnetic fields inside the chiral medium are governed by Maxwell equations together with the Drude-BornFedorov equations. We simplify the problem to a two-dimensional scattering problem and discuss the existence and the uniqueness of solutions by an integral equation approach. We show that for all but possibly a discrete set of wave numbers, the integral equation has a unique solution.展开更多
This paper is concerned with the electromagnetic scattering by a nonperfectly conductor obstacle in chiral environment. A two-dimensional mathematical model is established. The existence and uniqueness of the problem ...This paper is concerned with the electromagnetic scattering by a nonperfectly conductor obstacle in chiral environment. A two-dimensional mathematical model is established. The existence and uniqueness of the problem are discussed by potential theory.展开更多
The polynomial chaos expansion(PCE)is an efficient numerical method for performing a reliability analysis.It relates the output of a nonlinear system with the uncertainty in its input parameters using a multidimension...The polynomial chaos expansion(PCE)is an efficient numerical method for performing a reliability analysis.It relates the output of a nonlinear system with the uncertainty in its input parameters using a multidimensional polynomial approximation(the so-called PCE).Numerically,such an approximation can be obtained by using a regression method with a suitable design of experiments.The cost of this approximation depends on the size of the design of experiments.If the design of experiments is large and the system is modeled with a computationally expensive FEA(Finite Element Analysis)model,the PCE approximation becomes unfeasible.The aim of this work is to propose an algorithm that generates efficiently a design of experiments of a size defined by the user,in order to make the PCE approximation computationally feasible.It is an optimization algorithm that seeks to find the best design of experiments in the D-optimal sense for the PCE.This algorithm is a coupling between genetic algorithms and the Fedorov exchange algorithm.The efficiency of our approach in terms of accuracy and computational time reduction is compared with other existing methods in the case of analytical functions and finite element based functions.展开更多
基金the National Natural Science Foundation of China(Grant Nos.61875133 and 11874269).
文摘We theoretically investigate the reflected spatial Imbert–Fedorov(IF)shift of transverse-electric(TE)-polarized beam illuminating on a bulk Weyl semimetal(WSM).The spatial IF shift is enhanced significantly at two different frequencies close to the epsilon-near-zero(ENZ)frequency,where large values of reflection coefficients|r_(pp)|/|r_(ss)|are obtained due to the ENZ response induced different rapid increasing trends of|r_(pp)|and|r_(ss)|.Particularly,the tunable ENZ effect with tilt degree of Weyl cones and Fermi energy enables the enhanced spatial IF shift at different frequencies.The enhanced spatial IF shift also shows the adjustability of WSM thickness,incident angle and Weyl node separation.Our findings provide easy and available methods to enlarge and adjust the reflected IF shift of TE-polarized light with a WSM.
基金the National Natural Science Foundation of China(Grant No.62075060)the Natural Science Foundation of Hunan Province(Grant No.2020JJ4033)+2 种基金the Research Foundation of Education Bureau of Hunan Province(Grant Nos.20A218 and 19A198)Science and Technology Plan Project of Hunan Province(Grant No.2019TP1014)the Hunan Province Innovation Foundation for Postgraduate Grant(Grant No.CX20211185)。
文摘We establish the beam models of Goos–H?nchen(GH)and Imbert–Fedorov(IF)effects in tilted Weyl semimetals(WSMs),and systematically study the influences of Weyl cone tilting and chemical potential on the GH and IF shifts at a certain photon energy 1.96 eV.It is found that the GH and IF shifts in tilted type-Ⅰand type-ⅡWSMs are both almost symmetric about the Weyl cone tilting.Meanwhile,the GH and IF shifts in type-I WSMs almost do not change with the tilt degree of Weyl cones,while those in type-ⅡWSMs are extremely dependent on tilt degree.These trends are mainly due to the nearly symmetric distribution of WSMs conductivities,where the conductivities keep stable in type-I WSMs and gradually decrease with tilt degree in type-II WSMs.By adjusting the chemical potential,the boundary between type-I and type-II WSMs widens,and the dependence of the beam shifts on the tilt degree can be manipulated.Furthermore,by extending the relevant discussions to a wider frequency band,the peak fluctuation of GH shifts and the decrease of IF shifts occur gradually as the frequency increases,and the performance of beam shifts at photon energy 1.96 eV is equally suitable for other photon frequencies.The above findings provide a new reference for revisiting the beam shifts in tilted WSMs and determining the types of WSMs.
基金The Special Funds for Major State Basic Research Projects (G1999032802) in China the NNSF (10076006) of China.
文摘In this paper, we consider the electromagnetic scattering from periodic chiral structures. The structure is periodic in one direction and invariant in another direction. The electromagnetic fields in the chiral medium are governed by the Maxwell equations together with the Drude-Born-Fedorov equations. We simplify the problem to a two-dimensional scattering problem and we show that for all but possibly a discrete set of wave numbers, there is a unique quasi-periodic weak solution to the diffraction problem. The diffraction problem can be solved by finite element method. We also establish uniform error estimates for the finite element method and the error estimates when the truncation of the nonlocal transparent boundary operators takes place.
基金The Special Funds for Major State Basic Research Projects (G1999032802) in China and the NNSF (10076006) of China.
文摘In this paper, we consider the electromagnetic scattering by a periodic chiral structure. The media is homogeneous and the structure is periodic in one direction and invariant in another direction. The electromagnetic fields inside the chiral medium are governed by Maxwell equations together with the Drude-BornFedorov equations. We simplify the problem to a two-dimensional scattering problem and discuss the existence and the uniqueness of solutions by an integral equation approach. We show that for all but possibly a discrete set of wave numbers, the integral equation has a unique solution.
基金The NSF (11001177) of ChinaSZU R/D Fund (201043) of China
文摘This paper is concerned with the electromagnetic scattering by a nonperfectly conductor obstacle in chiral environment. A two-dimensional mathematical model is established. The existence and uniqueness of the problem are discussed by potential theory.
基金funding from the Walloon region of Belgium,convention number 5856,subvention FIRST-ENTREPRISE.
文摘The polynomial chaos expansion(PCE)is an efficient numerical method for performing a reliability analysis.It relates the output of a nonlinear system with the uncertainty in its input parameters using a multidimensional polynomial approximation(the so-called PCE).Numerically,such an approximation can be obtained by using a regression method with a suitable design of experiments.The cost of this approximation depends on the size of the design of experiments.If the design of experiments is large and the system is modeled with a computationally expensive FEA(Finite Element Analysis)model,the PCE approximation becomes unfeasible.The aim of this work is to propose an algorithm that generates efficiently a design of experiments of a size defined by the user,in order to make the PCE approximation computationally feasible.It is an optimization algorithm that seeks to find the best design of experiments in the D-optimal sense for the PCE.This algorithm is a coupling between genetic algorithms and the Fedorov exchange algorithm.The efficiency of our approach in terms of accuracy and computational time reduction is compared with other existing methods in the case of analytical functions and finite element based functions.
