We address the enhancement of electron drift in semiconductor superlattices of nanometre scale that occurs in combined electric and tilted magnetic fields if Bloch oscillations become resonant with cyclotron rotation in the transverse plane. We uncov
er the true dynamical mechanism of the phenomenon: the electron dynamics at relevant time-scales is regular or almost regular, contrary to the widespread belief that the enhancement arises through chaotic diffusion between collisions. The theory provides an accurate description of earlier numerical simulations, predicts new remarkable features verified by simulations, and suggests new ways of controlling resonant transport.
We develop a new approach to the theoretical treatment of the separatrix chaos, using a special analysis of the separatrix map. The approach allows us to describe boundaries of the separatrix chaotic layer in the Poincar{e} section and transport with
in the layer. We show that the maximum which the width of the layer in energy takes as the perturbation frequency varies is much larger than the perturbation amplitude, in contrast to predictions by earlier theories suggesting that the maximum width is of the order of the amplitude. The approach has also allowed us to develop the self-consistent theory of the earlier discovered (PRL 90, 174101 (2003)) drastic facilitation of the onset of global chaos between adjacent separatrices. Simulations agree with the theory.
