Magnetic forces and localized resonances in electron transfer through quantum rings

Abstract

Abstract. We study the current flow through semiconductor quantum rings. In high magnetic field the current is usually injected to the arm of the ring preferred by classical magnetic forces. However, for narrow magnetic field intervals that appear periodically on the magnetic field scale the current is injected to the other arm of the ring. We indicate that the appearance of the anomalous -non-classical -current circulation results from Fano interference involving localized resonant states. The identification of the Fano interference is based on the comparison of the solution of the scattering problem with the results of the stabilization method. The latter employs the bound-state type calculations and allows to extract both the energy of metastable states localized within the ring and the width of resonances by analysis of the energy spectrum of a finite size system in function of its length. The Fano resonances involving states of anomalous current circulation become extremely narrow on both magnetic field and energy scales. This is consistent with the orientation of the Lorentz force that tends to keep the electron within the ring and thus increases the lifetime of the electron localization within the ring. Absence of periodic Fano resonances in electron transfer probability through a quantum ring containing an elastic scatterer is also explained.arXiv:1011.1730v1 [cond-mat.mes-hall]

Spin-active devices based on graphene/WSe2 heterostructures

“…For high energies the spectra in the ring of suspended graphene and graphene on WSe 2 are very close to each other. The spectrum has two series of periodic levels, with energies decreasing (growing) with magnetic field, which correspond to the states associated with a clockwise (anticlockwise) current in the ring and are localized near the outer (inner) edge of the ring [44,45] and having angular momentum parallel (antiparallel) to the external magnetic field [45,46]. In both series of states the spin is parallel to the z direction.The width of those states is of the order of 10 nm at φ = 0.0008φ 0 and decreases with growing magnetic field.…”

Fano resonances in hexagonal zigzag graphene rings under external magnetic flux

“…The transmission function exhibits an asymmetric line shape which depends on the coupling between resonant and extended states. In particular, Fano resonances have been reported in semiconducting ring shaped structures under the presence of an * daiara@if.uff.br external magnetic field [24]. The resonances arise as consequence of the broken time-reversal symmetry of localized states and their interference with extended states through the semiconducting ring.…”

Localized states in a semiconductor quantum ring with a tangent wire

“…Recent studies [37][38][39] for a ring attached to the wire showed the existence of bound states, which are bounded in the ring but with small amplitude at the intersection and almost no amplitude along the wire. However, this kind of bound state is not the localized state as we mentioned above.…”