Inherent 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. This contribution remains nonzero even in isotropic nonmagnetic homogeneous systems. 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 in metals. This inherent mechanism thereby opens opportunities for probing electronic properties in materials through Kerr spectroscopy.