Strong nonlinear effects in conductivity of thin metallic samples (Review Article)

A series of works, dealt with nontrivial nonlinear stationary and nonstationary phenomena accompanying the flow of the transport current through thin pure single-crystal samples of metals at low temperatures, are discussed. The mechanism of the nonlinearity is magnetidynamical and related with an effect of the intrinsic magnetic field of the current on electron trajectories and, thus, on metal conductivity. The magnetodynamic nonlinearity leads to the nontrivial effect of drop of the resistance in thin samples with increasing the current. At high currents when a radius of curvature of electron trajectories in the intrinsic field of the current becomes smaller than cross sectional dimensions the effect of pinching of the current appears (pinch effect). In this case with increasing the current, the drop of the resistance is replaced by its increase. Experimental investigations of nonlinear current-voltage characteristics of thin cadmium and tungsten samples are also discussed. In these experiments, not only predictions of the theory are confirmed but new nonlinear effects accompanying the flow of strong currents were found. In particular, generation of self-oscillations of voltage in the regime of a given current was found. With increasing the current, the spectrum of the self-oscillations evolves, following a determined scenario with the transition from discrete to continuous, that indicates the appearance of a chaotic regime. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3672651]