Theoretical modeling of coherent ultrafast spinlight interactions: From one to many-electron systems

In this contribution we review some theoretical efforts performed in our group and devoted to the description, from first-principles, of the coherent ultrafast spin-light interactions. Based on the semi-relativistic expansion of the Dirac equation, we started by investigating the cases of one, two and many electrons (in the mean-field approximation) systems knowing that our main purpose is to realistically describe the nonlinear electron and spin dynamics of a quantumrelativistic system of many interacting electrons excited by an intense and ultrashort electromagnetic field. In addition to that, a classical and macroscopic model based on the an-harmonic Drude-Voigt model and the Maxwell’s equations was also developed for modeling ultrafast nonlinear coherent magneto-optical experiments performed on ferromagnetic thin films.