Spin Dynamics Of The Kapitza-Dirac Effect In Two-dimensional Spac

The Kapitza-Dirac effect is a special phenomenon of the interaction of an in-tense laser field with electrons,which diffract in a standing wave formed by two beams of coherent light propagating in opposite directions.Some theories predict that in the Bragg scattering mechanism of the Kapitza-Dirac effect,the electrons may undergo a spin-flip phenomenon.In previous theoretical studies of the spin effect,perturbation theory is usually used,and for the description of the potential field a discrete plane-wave approximation is used,whose computational accuracy is challenged.My work develops the study of spin effects in the Kapitza-Dirac effect on this basis.We realize the first numerical simulation of the Kapitza-Dirac effect to show the reader the electron motion process in this effect in the most intuitive way within two dimensional area.Not only in the Bragg scattering regime,we simulate the elec-tron spin dynamics in higher order diffraction regimes.Meanwhile,for the standing wave potential field description,instead of adopting a simple one-dimensional plane wave approximation,we choose a more realistic Gaussian beam standing wave po-tential field,which takes into account the two-dimensional spatial field envelope without any approximation to improve its computational accuracy.In addition,unlike the specific parameters used in previous theoretical studies,we consider the influence of a certain range of Gaussian beam divergence and wave number on the electron spin effect under the variation of the potential field parameters and inves-tigate the influence of the longitudinal component of Gaussian light on the spin effect.Ultimately we conclude that spin effects are prevalent in the Kapitza-Dirac effect,and the spin of diffracted electron will be flipped in varying degrees within all the three regimes,with the most pronounced spin flip in the Bragg scattering mechanism.with changing the parameters of Gaussian beam,the beam divergence becomes large(?>0.1)will destroy the Bragg scattering regime effect,and the probability of spin flipping is directly proportional to the square of the product of the wave number and the reciprocal of the beam divergence(k_L/?)~2in Gaussian beam.In the case that the plane wave approximation with small divergence is not completely destroyed,the influence of the longitudinal component of the Gaussian light in the Bragg scattering mechanism on the spin effect is negligible.