Tuning Fano resonances by magnetic forces for electron transport through a quantum wire side coupled to a quantum ring

Abstract

We consider electron transport in a quantum wire with a side-coupled quantum ring in a twodimensional model that accounts for a finite width of the channels. We use the finite difference technique to solve the scattering problem as well as to determine the ring-localized states of the energy continuum. The backscattering probability exhibits Fano peaks for magnetic fields for which a ring-localized states appear at the Fermi level. We find that the width of the Fano resonances changes at high magnetic field. The width is increased (decreased) for resonant states with current circulation that produce the magnetic dipole moment that is parallel (antiparallel) to the external magnetic field. We indicate that the opposite behavior of Fano resonances due to localized states with clockwise and counterclockwise currents results from the magnetic forces which change the strength of their coupling to the channel and modify the lifetime of localized states.

Aharonov-Bohm interferometer based onn−pjunctions in graphene nanoribbons

“…In the present results all periodic structures in conductance become thinner at high magnetic field, and the energies of the lines grow with the magnetic field since the dipole moment generated by the current in the resonant states is opposite to the external magnetic field. In contrast to the rings with tailored confinement [66] no periodic lines with energies that fall in B and increase in width are found. This is because the n-p junction at B > 0 supports confinement of counterclockwise currents only, while the tailored rings host currents of both orientations.…”

“…The edge current that is coupled to the n-p junction by the tip forms a system geometrically related to a quantum dot [64] or a quantum ring [65] singly connected to the channel. The conductance of these systems is governed by Fano interference effects, which for quantum rings [66] produce resonances of width (lifetime) which is reduced or increased by the external magnetic field depending on the orientation of the current circulation around the ring. The stabilization of the resonant lifetime [66] is due to the classical Lorentz force which modifies localization of the currents at the edges of the sample.…”

“…The conductance of these systems is governed by Fano interference effects, which for quantum rings [66] produce resonances of width (lifetime) which is reduced or increased by the external magnetic field depending on the orientation of the current circulation around the ring. The stabilization of the resonant lifetime [66] is due to the classical Lorentz force which modifies localization of the currents at the edges of the sample. The orientation of the circulating current determines the projection of the produced magnetic moment with the external magnetic field leading to a growth or reduction of the resonance energy with B [60], for the produced magnetic dipole aligned antiparallel or parallel to the external magnetic field vector, respectively.…”

Magnetic field-induced control of transport in multiterminal focusing quantum billiards

“…6(b)(iii) and (iv)], mediated by edge states that are localized on the disk edges (similar to the states leading to sharp reflection resonances, due to different geometrical setup, in Ref. 49). The effective resonator length is, approximately, the mean periphery 2π(r + w/3), leading to the observed peak spacing ∆κ ≈ 0.247 in (b)(iv).…”

Spectral and localization properties of the Dirichlet wave guide with two concentric Neumann discs

“…Anticrossings very similar to the ones discussed above were calculated for the magnetic quantum ring [55] when the increasing inner radius of the field-free annulus in the otherwise uniform magnetic field for the large fixed values of its outer counterpart forms the avoided crossings of the energies of the adjacent states with the same azimuthal quantum number m. The passage through the energy anticrossing in this case is accompanied by the abrupt change of the corresponding whirling persistent current of the same quantum mechanical state which draws the very clear parallel to our geometry with the rapid variations of the mean radius r. This similarity becomes almost complete if one recalls that the azimuthal current in the uniform magnetic field is determined by the expression from the right-hand side of equation ( 31) [55]. Energy anticrossings present a ubiquitous feature of the energy spectrum of the quantum systems with finite height potentials [56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] and are indispensable, for example, in the description of the quantum Hall effect [67].…”