Abstract. The effect of the external magnetic field on the spectral properties of one-electron non-uniform quantum ring with radially directed hills is analysed. The corresponding oneparticle wave equation is separable in the adiabatic limit, when the layer thickness is essentially smaller than its lateral dimension. Our calculations show that the presence of a single axially directed hill as well as a rise of the central hole thickness produce a quenching of the AharonovBohm (AB) oscillations of the lower energy levels and of the magnetic momentum. However, as the number of radially directed hills is increased, the system exhibits again oscillations, resulted from an enhancement of tunnelling circular currents.
IntroductionThe development of new semiconductor growth techniques has made possible the fabrication of the selfassembled quantum rings (QRs) which in the presence of the magnetic field exhibit an interesting quantum-interference phenomenon, denominated AB effect [1]. Theoretical analysis of this phenomenon reveals its delicate nature related to a destructive interference induced by a possibility to appearance of multiple different spatially separated paths in QR under a diminishing of the central-hole dimension or any non-uniformity that breaks the axial symmetry [2,7]. This destructive interference disappears if the ring is sufficiently narrow, and uniform. However, further numerical analysis of more realistic 3D model of non-uniform crater-like QRs shows that, although the real QR shape differs strongly from an idealized circular-symmetric narrow ring structure, AB-type oscillations in the magnetization survive [8,10]. A 3D exactly solvable model of the crater-like one-electron QR, proposed recently in reference [11,12] provides an explanation of the stability of the AB oscillations with respect to structural nonuniformities. In the presence of the magnetic field applied along the symmetry axis, more probable electron paths in this model are clustered close to the crater's rim being similar to those in quasi-onedimensional quantum rings independently on the crater width. However, any slight non-uniformity produced by a single radially directed valley or single hill suppresses the oscillations of several lower levels due to the localization of the corresponding rotational states. Nevertheless, when the nonuniformity becomes substantial due to the presence of multiple valleys and hills, the AB oscillations generated by the external magnetic field becomes again possible owing to the electron tunnelling through thin potential barriers.It is possible to extend the model considered in reference [11,12] in order to analyse additionally the effect of the variation of the width and the depth of the central-hole on the AB oscillations. In this extended model, proposed in this paper, the crater's height between the central hole and the outer border