QUANTUM TRANSPORT ANOMALIES IN SEMICONDUCTOR NANOSYSTEMS

We present quantum transport anomalies in the theoretical conductance of various semiconductor nanostructures. We first investigate a quantu m channel with a chain of quantum boxes connected by slits, called a s uperlattice structure, and study the miniband and minigap effects asso ciated with resonances and anti-resonances in the conductance. We also report studies of electron transport in a quantum wire containing ser ies or parallel slits and a detector slit. In these systems, strong co nductance oscillations due to quantum interference effects are predict ed as a detector slit is moved across the wire. In the case of a singl e and multi-series slits, we attribute these effects to multiple refle ctions of the phase-coherent electron along the quantum wire. The tran smission coefficients and electronic phase shifts are examined, which provide insights into the origins of these conductance oscillations. I n the case of multi-parallel slits, peaks with two- (four-) fold split ting in the conductance are exhibited due to the quantum branch interf erence between the two (four) alternative electron paths. We also stud y the conductance of a quantum structure containing an artificially pr oduced impurity. It is shown that the conductance modulations are stro ng when the impurity is scanned across the channel. We explain these o scillatory features of the conductance by a simple optical interferenc e model and a simple adiabatic model. (C) 1995 American Institute of P hysics.