Conductance and persistent current of a quantum ring coupled to a quantum wire under external fields

The electronic transport of a noninteracting quantum ring side coupled to a quantum wire is studied via a single-band tunneling tight-binding Hamiltonian. We found that the system develops an oscillating band with antiresonances and resonances arising from the hybridization of the quasibound levels of the ring and the coupling to the quantum wire. The positions of the antiresonances correspond exactly to the electronic spectrum of the isolated ring. Moreover, for a uniform quantum ring the conductance and the persistent current density were found to exhibit a particular odd-even parity related with the ring order. The effects of an in-plane electric field were also studied. This field shifts the electronic spectrum and damps the amplitude of the persistent current density. These features may be used to control externally the energy spectra and the amplitude of the persistent current.