Electronic properties of superlattices on quantum rings
JOURNAL OF PHYSICS-CONDENSED MATTER, (2017)DOI: 10.1088/1361-648X/aa617e
Zusammenfassung
We present a theoretical study of the one-electron states of a
semiconductor-made quantum ring (QR) containing a series of
piecewise-constant wells and barriers distributed along the ring
circumference. The single quantum well and the superlattice cases are
considered in detail. We also investigate how such confining potentials
affect the Aharonov-Bohm like oscillations of the energy spectrum and
current in the presence of a magnetic field. The model is simple enough
so as to allow obtaining various analytical or quasi-analytical results.
We show that the well-in-a-ring structure presents enhanced localization
features, as well as specific geometrical resonances in its
above-barrier spectrum. We stress that the superlattice-in-a-ring
structure allows giving a physical meaning to the often used but usually
artificial Born-von-Karman periodic conditions, and discuss in detail
the formation of energy minibands and minigaps for the circumferential
motion, as well as several properties of the superlattice eigenstates in
the presence of the magnetic field. We obtain that the AharonovBohm
oscillations of below-barrier miniband states are reinforced, owing to
the important tunnel coupling between neighbour wells of the
superlattice, which permits the electron to move in the ring.
Additionally, we analysis a superlattice-like structure made of a
regular distribution of ionized impurities placed around the QR, a
system that may implement the superlattice in a ring idea. Finally, we
consider several random disorder models, in order to study roughness
disorder and to tackle the robustness of some results against deviations
from the ideally nanostructured ring system.