The nonlinear effect of transport current on the response of metals to electromagnetic radiation

The nonlinear interaction of a direct current (DC) flowing in a thin metal film with an external low-frequency alternating-current (AC) electromagneti c held is studied theoretically. The nonlinearity is related to the influen ce of the magnetic field of the DC and the magnetic field of the wave on th e form of the electron trajectories. This magnetodynamic mechanism of nonli nearity is typical for pure metals at low temperatures. We find that such a n interaction causes sharp kinks in the temporal dependence of the AC elect ric held of the wave on the surface of a sample. The phenomenon of amplific ation of the electromagnetic signal on the metal surface is predicted. We a lso calculate the nonlinear surface impedance and show that it decreases dr astically with the increase of the wave amplitude.