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 THz pulse. The response of two models, a continuous and 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. 
Sigridur Sif Gylfadottir, Marian Nita, Vidar Gudmundsson, and Andrei   Manolescu