Intrinsic Electro-Optic Kerr Rotation

We uncover a previously overlooked contribution to the electro-optic Kerr rotation of reflected light, arising from the interplay of matter, the static electric field, and the magnetic component of light. Remarkably, this mechanism dominates in isotropic nonmagnetic homogeneous metals. We derive analytical expressions for the Kerr rotation in both two-dimensional layers and semi-infinite systems. Within the relaxation-time approximation, we predict experimentally accessible signal magnitudes. This intrinsic mechanism thereby opens new opportunities for probing electronic properties in materials through Kerr spectroscopy.