Numerical simulation of ballistic magnetoconductance and magnetic focusing in strained Si-SiGe cavities

摘要

We present numerical simulations of the transport properties of a ballistic cavity connected to two leads in the presence of a finite degree of decoherence. The cavity is obtained by realizing a 'quantum chicane', i.e., by shifting a short section of a quantum wire defined by etching on a SiGe heterostructure. We compare our results with experiments by Scappucci et al (2004 Trends in Nanotechnology (Segovia, Spain, Sept. 2004) unpublished) and show that the magnetoconductance features can be reproduced if we use a recently developed model that includes decoherence with a phenomenological statistical description. Otherwise, simulations based on completely coherent transport would provide a much richer structure of magnetoconductance, that in experiments is smoothed out by dephasing processes. In particular, we recover experimental features of the magnetoconductance such as magnetic focusing and Shubnikov-de Haas oscillations. By computing the local partial density of states of the system at different values of the external field we recover the semiclassical orbits.