Spin effects in Kapitza-Dirac scattering at light with elliptical polarization

TL;DR

This paper investigates spin effects in Kapitza-Dirac electron scattering with elliptical polarization, revealing spin precession phenomena in specific polarization configurations through numerical and analytical solutions.

Contribution

It demonstrates how elliptically polarized light influences electron spin dynamics in the Kapitza-Dirac effect, highlighting conditions for observable spin precession.

Findings

Spin precession occurs when electric-field components have the same sense of rotation.

No spin effects are observed with opposite sense of rotation, resulting in linear polarization.

Numerical and analytical methods confirm the spin dynamics under different polarization setups.

Abstract

The Kapitza-Dirac effect, which refers to electron scattering at standing light waves, is studied in the Bragg regime with counterpropagating elliptically polarized electromagnetic waves with the same intensity, wavelength, and degree of polarization for two different setups. In the first setup, where the electric-field components of the counterpropagating waves have the same sense of rotation, we find distinct spin effects. The spins of the scattered electrons and of the nonscattered electrons, respectively, precess with a frequency that is of the order of the Bragg-reflection Rabi frequency. When the electric-field components of the counterpropagating waves have an opposite sense of rotation, which is the second considered setup, the standing wave has linear polarization, and no spin effects can be observed. Our results are based on numerical solutions of the time-dependent Dirac equation and the analytical solution of a relativistic Pauli equation, which accounts for the leading relativistic effects.