Macroscopic drift current in the inverse Faraday effect

The inverse Faraday effect (IFE) describes the spontaneous magnetization of a conducting or dielectric medium due to irradiation with a circularly polarized electromagnetic wave. The effect has recently been discussed in the context of laser-induced magnetic switching of solids. We analyze analytically the electron dynamics induced by a circularly polarized laser beam within the framework of plasma theory. A macroscopic drift current is obtained, which circulates around the perimeter of the laser beam. The magnetic moment due to this macroscopic current has an opposite sign and half of the magnitude of the magnetic moment that is generated directly by the IFE. This constitutes an important contribution of angular momentum transferred from the wave to the medium and a classical mechanism for the light-induced generation of magnetic fields.

Figure 1

Normalized Gaussian field amplitude $E\left(r\right)$ and normalized magnitude of the drift current density $j_{\varphi }\left(r\right)$ as a function of the distance $r$ from the center of the beam, measured in units of the beam waist $w$. The current flows circularly around the $r=0$ axis with helicity-dependent sign.