We report electronic transmission properties of a simple tight binding Aharonov-Bohm ring threaded by a magnetic flux, to one arm of which a finite cluster of atoms has been attached from one side. We demonstrate that, by suitably choosing the number of scatterers in each arm of the quantum ring, the transmission across the ring can be completely blocked when the ring is decoupled from the atomic cluster and the flux threading the ring becomes equal to half the fundamental flux quantum. A novel transmission resonance then occurs immediately as the coupling between the ring and the impurity cluster is switched 'on'. It is shown that the delta-like transmission resonances occur precisely at the eigenvalues of the side coupled chain of atoms. The 'switching' effect can be observed either for all the eigenvalues of the isolated atomic cluster, or for a selected set of them, depending on the number of scatterers in the arms of the ring. The ring-dot coupling can be gradually increased to suppress the oscillations in the magneto-transmission completely. However, the suppression can lead either to a complete transparency or no transmission at all, occasionally accompanied by a reversal of phase at special values of the magnetic flux.

We present exact results on certain electronic properties of an anisotropic Sierpinski gasket fractal. We use a tight binding Hamiltonian and work within the formalism of a real space renormalization group (RSRG) method. The anisotropy is introduced in the values of the nearest neighbor hopping integrals. An extensive numerical examination of the two terminal transmission spectrum and the flow of the hopping integrals under the RSRG iterations strongly suggest that an anisotropic gasket is more conducting than its isotropic counter part and that, even a minimal anisotropy in the hopping integrals generate continuous bands of eigenstates in the spectrum for finite Sierpinski gaskets of arbitrarily large size. We also discuss the effect of a magnetic field threading the planar gasket on its transport properties and calculate the persistent current in the system. The sensitivity of the persistent current on the anisotropy and on the band filling is also discussed.

We propose a simple model of two coupled mesoscopic rings threaded by magnetic flux which mimics a device for electron transmission in a controlled fashion. Within a tight binding formal-

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We investigate the two-terminal electronic transport of a model mesoscopic ring threaded by a magnetic flux and embedded in between two semi-infinite metallic electrodes. The ring is locally distorted to bring a pair of atomic sites residing in the two opposite arms into close proximity. The proximity of the two atoms is modeled by an inter-arm tunnel hopping matrix element, and is shown to lead to nontrivial features in the transmission and the density of states of the system. The asymmetric Fano lineshape and its reversal, the Aharonov–Bohm oscillations in the conductance and the device aspect of the system are critically examined.