Speaker
Description
The Floquet theory of time-periodic systems provides a middle ground between equilibrium and far-from-equilibrium physics, making it ideal for studying non-equilibrium steady states. We employ this framework to interacting electrons exposed to spatially and time-periodic potentials by combining Floquet theory with RPA and GW. This is applied to both the homogeneous electron gas under moving optical lattice and monolayer Graphene under circularly polarized light, allowing us to resolve the interplay between periodic driving, electronic correlations, and collective charge excitations. We compute Floquet-induced Greens function, dielectric function, and self-energy; and demonstrate the formation of Bloch-Floquet sidebands in the electronic spectral function and in direct and inverse photoemission spectra. The periodic modulation further induces plasmonic sidebands and generates additional Floquet-umklapp regions for the electron-hole continuum. Our analysis highlights how periodic drive controls the redistribution of spectral weight and the renormalization of collective modes. This framework provides a route for predicting the plasmonic and optical response properties of weakly to moderately correlated materials under periodic laser driving.