Two-dimensional simulation of the spin-flip in the Kapitza-Dirac effect

TL;DR

This paper presents a detailed two-dimensional relativistic simulation of the Kapitza-Dirac effect, demonstrating the possibility of spin-flip phenomena and analyzing the impact of realistic laser beam properties on electron diffraction.

Contribution

It introduces a non-approximated, two-dimensional Dirac equation simulation of the Kapitza-Dirac effect, including spin dynamics and beam focusing effects.

Findings

Spin-flip in the Kapitza-Dirac effect is possible.

Plane wave approximation validity is discussed.

Higher order diffraction peaks are analyzed.

Abstract

Many calculations in strong field quantum field theory are carried out by using a simple field geometry, often neglecting the spacial field envelope. In this article, we simulate the electron diffraction quantum dynamics of the Kapitza-Dirac effect in a Gaussian beam standing light wave. The two-dimensional simulation is computed in a relativistic framework, by solving the Dirac equation with the fast Fourier transform split operator method. Except the numerical propagation method, our results are obtained without applying approximations and demonstrate that a spin-flip in the Kapitza-Dirac effect is possible. We further discuss properties, such as the validity of a plane wave approach for the theoretical description, the influence of the longitudinal polarization component due to laser beam focusing and higher order diffraction peaks in Kapitza-Dirac scattering.