Electron-spin dynamics in elliptically polarized light waves

TL;DR

This paper explores how elliptically polarized light interacts with free electrons, causing spin precession through a coupling similar to spin-orbit interaction, analyzed via numerical and perturbative relativistic methods.

Contribution

It demonstrates the coupling mechanism between light's spin angular momentum and electron spin, providing a detailed analysis using both relativistic and nonrelativistic approaches.

Findings

Spin precession frequency depends on laser intensity and spin density.

Coupling mechanism is similar to spin-orbit interaction.

Relativistic and nonrelativistic models agree on key dynamics.

Abstract

We investigate the coupling of the spin angular momentum of light beams with elliptical polarization to the spin degree of freedom of free electrons. It is shown that this coupling, which is of similar origin as the well-known spin-orbit coupling, can lead to spin precession. The spin-precession frequency is proportional to the product of the laser-field's intensity and its spin density. The electron-spin dynamics is analyzed by employing exact numerical methods as well as time-dependent perturbation theory based on the fully relativistic Dirac equation and on the nonrelativistic Pauli equation that is amended by a relativistic correction that accounts for the light's spin density.