Analysis of Photo-Induced Chirality and Magnetic Toroidal Moment Based on Floquet Formalism

We analyze the condition of photo-induced atomic-scale chirality and magnetic toroidal moment. By performing a high-frequency expansion in the Floquet formalism, we derive an effective static model Hamiltonian from the spinful s-p hybridized model of a single atom interacting with an electromagnetic wave with a particular polarization. The lowestorder and third-order contributions in the high-frequency expansion give rise to the coupling to induce an electric toroidal monopole corresponding to microscopic chirality, while the second-order contribution provides the coupling to induce a magnetic toroidal dipole. We also discuss the condition of the polarization of the electromagnetic wave and induced multipoles. Our results stimulate a new direction of controlling unconventional multipoles by electromagnetic waves.