Driving collective current oscillations using light: The time-dependent GW approach

Electron-electron interactions in solids give rise to longitudinal collective charge excitations known as plasmons, which are observable corresponding to resonances in the density-density response function of the electrons. In this study, we solve the Kadanoff-Baym equations within the non-equilibrium two-time GW approach for sodium metal and demonstrate that current-current interactions can induce a novel type of collective excitation, which we term as "curron." By taking into account the self-consistent interaction between the vector potential generated by electronic currents and the vector potential driving them, we construct a system of interacting currents mediated by vector potentials. We show that this leads to the emergence of a quasiparticle associated with transverse collective current oscillations, corresponding to resonances in the current-current response function.