One-dimensional wave equation for two electrons in nanoring whose height and width are much smaller than the diameter is derived. The energies of the two-electron low-lying states arising from the twoelectron rotation around the axis and their dependencies on the nanoring diameter, height and width are analysed. The level-ordering and crossovers of the corresponding curves related to the strong electronelectron interaction are studied and discussed. In the limit case as the height and width of the ring tend to zero our results coincide with those obtained previously for a one-dimensional nanoring.1 Introduction The understanding of the energy spectrum of few-electron quantum dots (QDs) is a key step toward the design of high performances devices. It is the reason why the energy spectrum of two electrons in QDs with parabolic or rectangular potential have been analysed by using different methods [1]. Commonly, QDs fabricated by using the Stranski-Krastanov method can have disk, lens or cone shape with circular top view cross section and a large area-to-height aspect ratio [2]. Recently, the realization of QDs with topology of a ring whose outer radius is between 30 and 70 nm, interior radius is about 10 nm and the height is between 2 and 4 nm, has been demonstrated [3], using the self-assembled techniques. The energy levels of two-electron quantum ring (QR) have been calculated and some differences and analogies between QDs and QRs have been discussed [4,5]. To analyse the electronic properties of QRs with two electrons a one-dimensional exactly solvable model which describes their rotation around the axis in the presence of the magnetic field, recently has been proposed [6]. In spite of that this model corresponds to a ring with infinite barrier potential and infinite radius-to-width aspect ratio, we consider that this exact solution could be used as starting point to analyse the electronic spectrum of more realistic two-electron QR models. In this paper we derive an equation for two-electron angular motion in a QR with a large radius-to-width aspect ratio and finite barrier potential within the framework of the adiabatic approximation applied previously to disk in Ref. [7]. We find that the parameters of this equation for a finite barrier potential depend strongly on the QR radius-to-width aspect ratio coinciding with those from Ref. [6] only when this ratio tends to zero and simultaneously the barrier potential tends to infinity. We present the results of calculation for the energies of several low-lying levels as a function of the QR radius and height. The analysis of the effect of the magnetic field on the two-electron ring energies is not included in the present work.

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Adopting a simple one-band tight-binding Hamiltonian and using the diagrammatic techniques for nonequilibrium processes proposed by Keldysh, we investigate the resonant tunneling transport properties through GaAs/Al x Ga 1Ϫx As double-barrier heterostructures under the action of in-plane and parallel magnetic field. The in-plane magnetic field leads to a shift to higher bias and a diminishing of the intensity of the resonant tunneling peak in the characteristic curves of current versus voltage in good agreement with experimental results. Also, we have found that the diminishing of the hopping energy between nearest neighbors is caused by the same effects as the in-plane magnetic field on the current-voltage characteristics. On the other hand, we have found that the intensity of the resonant peaks increases when the magnetic field is applied parallel to the current direction, an expected result due to the increasing values of the magnitude of the hopping parameter with the magnetic field. Our results compare quite well with experimental reports.

PAMELA: An open-source software package for calculating nonlocal exact exchange effects on electron gases in core-shell nanowires AIP Advances 2, 032173 (2012) Tunable electronic transport characteristics through an AA-stacked bilayer graphene with magnetoelectric barriers J. Appl. Phys. 112, 053714 (2012) Pinned interface dipole-induced tunneling electroresistance in ferroelectric tunnel junctions: A theoretical investigation J. Appl. Phys. 112, 054104 (2012) Current-voltage characteristics and ON/OFF ratio in ferroelectric tunnel junctions J. Appl. Phys. 112, 054102 (2012) Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions AIP Advances 2, 032155 (2012) Additional information on J. Appl. Phys.

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By means of the diagrammatic techniques for nonequilibrium processes proposed by Keldysh and adopting a simple one-band tight-binding Hamiltonian, we study the resonant tunneling in GaAs/ Al x Ga 1 À x As double-barrier heterostructures (DBH) in the presence of a magnetic field applied parallel to the current direction in this work. We have found that the number of Landau levels that contribute to the resonant tunneling diminishes with the magnetic field, all centered around the position of the resonance. Also, we have calculated the conductance versus bias voltage and we have found that the maxima and minima of the conductance move towards higher bias with the magnetic field in good agreement with experimental reports. We have considered the effects of isoelectronic impurity-planes localized at the well region on the J-V characteristics of the system and on the conductance versus voltage. The presence of the impurity-plane induces a shift to higher (lower) energies of the density of states, of the J-V characteristic curves and of the conductance versus voltage, corresponding to a repulsive (attractive) potential.

Theoretical research on electronic properties in mesoscopic condensed matter systems has focused primarily on the electron charge freedom degrees, while its corresponding spin Keldysh also a simple one-band tight-binding Hamiltonian is adopted in the theoretical framework. We have compared our results of the spin-tunneling with previous ones reported in literature.