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

It is well known that electron-electron interactions generate longitudinal collective charge excitations known as plasmons, which correspond to resonances in the electron density-density response function. In this work, using the non-equilibrium real-time GW approach that includes the full two-time self-energy, we show that the current-current interactions can drive a different kind of collective excitation. These transverse collective current excitations lead to resonances in the current-current response function. We also propose routes for their experimental detection.