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The dominant noise source, which effects the electron dynamics in semiconductor nano-structures, is shot noise, which is associated with the tunneling of individual carriers across a potential barrier. We consider noise-induced dynamics of electrons in a superlattice, which consists of alternating layers of two semiconductor materials with different band gaps. The parameters are fixed in the regime below the Hopf bifurcation of spatio-temporal oscillations, where in the absence of noise the system rests in a fixed point. It is shown that in this case noise applied to the superlattice can induce quite coherent oscillations of the current through the device. While the regularity of these oscillations depends on the noise intensity, their dominant frequency remains almost constant with variation of the noise level in the system. Further, we demonstrate that a time-delayed feedback scheme that was previously used to control purely temporal oscillations induced by noise, can not only enhance or deteriorate the regularity of stochastic spatio-temporal patterns but also allows for the manipulation of the system’s timescales with varying time delay. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The electronic transport through two coupled quantum dots in series can be described either in a fully coherent approach (e.g. density matrix description or nonequilibrium Green’s functions) or in a simple sequential tunneling treatment (Pauli master equation with Fermi’s Golden rule for coupling between the quantum dots). It turns out that both descriptions provide the same average current for noninteracting electrons. In contrast, the zero-frequency spectral power density and the skewness are different for intermediate coupling strengths between the quantum dots reflecting their sensitivity on coherence in the tunneling process. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]