Microscopic theory of the inverse Faraday effect in a multiorbital model: Role of orbital magnetic moment and electric dipole

Abstract: We theoretically investigate the inverse Faraday effect (IFE), a phenomenon where circularly-polarized light induces a magnetic moment, in a multiorbital metallic system. We demonstrate that the total magnetic moment can be decomposed into several contributions in multiorbital tight-binding models. In particular, we reveal that the electric dipole moment of Wannier orbitals also contributes to the orbital magnetic moment, which is not included in the conventional expression for the orbital magnetic moment in lattice systems. To account for all possible contributions, we adopt an $s$-$p$ tight-binding system as a minimal model for the IFE. Using an analytical approach based on the Schrieffer-Wolff transformation, we clarify the physical origins of these contributions. Additionally, we quantitatively evaluate each contribution on an equal footing through a numerical approach based on the Floquet formalism. Our results reveal that the orbital magnetic moment exhibits a significantly larger response compared to the spin magnetic moment, with all contributions to the orbital magnetic moment being comparable in magnitude. These findings highlight the essential role of orbital degrees of freedom in the IFE.