Use of stochastic web patterns to control electron transport in semiconductor superlattices

Chaotic electron transport has been explored in a variety of semiconductor structures in which the transition to chaos occurs by the gradual and progressive destruction of stable orbits in response to an increasing perturbation. There is also a much rarer type of chaos, known as non-KAM dynamics, which switches on and off abruptly when the temporal frequency of the perturbation reaches certain critical values. This type of chaotic motion is of great interest due to diverse applications in the theory of plasma physics, tokamak fusion, turbulent fluid dynamics, ion traps, and quasicrystals, but has not yet been realized in experiment. Here, we show that electrons in a superlattice miniband with a tilted magnetic field provide an experimentally-accessible non-KAM system and, moreover, that this unusual type of chaotic dynamics can produce strong resonant enhancement of the electron drift velocity. The onset of chaos is characterized by the formation of intricate “stochastic web” patterns in the electron phase space. These webs delocalize the electron orbits, thereby generating strong resonant peaks in our calculated drift velocity versus electric field characteristics.