Magnetic forces and localized resonances in electron transfer through quantumrings

Abstract

We study the current flow through semiconductor quantum rings. In high magnetic fieldsthe current is usually injected into the arm of the ring preferred by classical magneticforces. However, for narrow magnetic field intervals that appear periodically on themagnetic field scale the current is injected into the other arm of the ring. We indicate thatthe appearance of the anomalous—non-classical—current circulation results from Fanointerference involving localized resonant states. The identification of the Fano interferenceis based on the comparison of the solution of the scattering problem with the results of thestabilization method. The latter employs the bound-state type calculations and allows us toextract both the energy of metastable states localized within the ring and thewidth of resonances by analysis of the energy spectrum of a finite size systemas a function of its length. The Fano resonances involving states of anomalouscurrent circulation become extremely narrow on both the magnetic field and energyscales. This is consistent with the orientation of the Lorentz force that tends tokeep the electron within the ring and thus increases the lifetime of the electronlocalization within the ring. Absence of periodic Fano resonances in electron transferprobability through a quantum ring containing an elastic scatterer is also explained.