Net current generation in a 1D quantum ring at zero magnetic field

We study a non-adiabatic excitation of an electron system in a 1D quantum ring radiated by a short terahertz pulse. The response of two models, a continuous and a discrete, is explored. By introducing a spatial asymmetry in the external perturbation, a net current can be generated in the ring at a zero magnetic field. Effect of impurities and ratchets are investigated in combination with symmetric and asymmetric external excitation.