Relativistic treatment of harmonics from impurity systems in quantum wires

Within a one-particle approximation of the Dirac equation we investigate a defect system in a quantum wire. We demonstrate that by minimally coupling a laser field of frequency $\omega$ to such an impurity system, one may generate harmonics of multiples of the incoming frequency. In a double defect system one may use the distance between the defects in order to tune the cutoff frequency.