We study, using numerical simulations, the transport and noise properties both of a series of barriers and of cascaded constrictions, comparing our results with the conclusions of previous analyses. In particular, we point out the differences existing between the case in which the barriers or the constrictions are evenly spaced and the case in which they are randomly spaced, proposing possible explanations for the observed phenomena.
We present simulations of the effects of dephasing on the shot
noise properties of mesoscopic coherent devices, such as chaotic
cavities and Aharonov-Bohm rings. We adopt a phenomenological
model that exploits the statistical nature of the dephasing
mechanism and is able to cover the intermediate regime between a
fully coherent and completely incoherent (i.e., semiclassical)
transport. By investigating conductance and noise properties as a
function of the dephasing length, we conclude that decoherence has
no specific effect on shot noise which can be distinguished from
the one it has on conductance. In addition, when a large number of
conducting channels is considered, semiclassical and quantum
behavior must converge, yielding as a consequence the independence
of DC and noise properties from dephasing.
A numerical approach for the evaluation of conductance and shot noise suppression in mesoscopic structures is presented and applied to a few relevant cases. Details are provided both of the technique based on a recursive Green's function procedure that is used for calculations in the absence of a magnetic field and of the recursive scattering matrix method that is applied to simulations with nonzero magnetic field. Shot noise suppression in cascaded chaotic cavities is studied and discussed in comparison with the suppression obtained for cascaded potential barriers. It is observed that the Fano factor for multiple cascaded cavities is the same as that for a single cavity, as long as its apertures are small compared to its width. Finally, a particular structure, consisting in a cavity with a central potential barrier, is studied and from its noise behavior conclusions are drawn about the very different role played by a constriction or by a potential barrier in the presence of edge states.
Conference Committee Involvement (1)
Noise and Fluctuations in Circuits, Devices, and Materials