Aram Manaselyan

Effect of the dielectric-constant mismatch and magnetic field on the binding energy of hydrogenic impurities in a spherical quantum dot

Abstract Within the effective mass approximation and variational method the effect of dielectric constant mismatch between the size-quantized semiconductor sphere, coating and surrounding environment on impurity binding energy in both the absence and presence of a magnetic field is considered. The dependences of the binding energy of a hydrogenic on-center impurity on the sphere and coating radii, alloy concentration, dielectric-constant mismatch, and magnetic field intensity are found for the GaAs–Ga 1− x Al x As–AlAs (or vacuum) system.

Enhanced Rashba effect for hole states in a quantum dot

The effect of Rashba spin-orbit (SO) interaction on the hole states in a quantum dot is studied in the presence of an external magnetic field. We demonstrate here that the Rashba SO coupling has a profound effect on the energy spectrum of the holes revealing level repulsions between the states with the same total momentum. We also show that the resulting spin-orbit gap is much larger than the corresponding one for the electron energy levels in a quantum dot. Inter-hole interactions only marginally reduce the spin-orbit gap. This enhanced Rashba effect would manifest itself in the tuneling current which depends on the spin-orbit coupling strength.

The mobility of charge carriers in a size-quantized coated semiconductor wire

Within the f ofa staircase in2nitely deep potential well model, the mobility ofcharge carriers is calculated f scattering on impurity centers located on the axis ofa size-quantized semiconducting coated wire. Calculations are done for the dielectric constant mismatch of the wire, coating and surrounding environment, taking into account the di5erence ofthe e5ective masses in the wire and coating. The e5ect ofa longitudinal magnetic 2eld on mobility is also considered. Numerical results are presented for the GaAs–Ga1−xAlxAs system at di5erent values ofthe wire and coating radii, the alloy concentration x, and magnetic 2eld. ? 2002 Elsevier Science B.V. All rights reserved.

Tunability of Raman spectral signatures by Rashba spin-orbit interaction in few-electron quantum dots

The resonant inelastic light scattering from a GaAs quantum dot containing a few electrons is investigated theoretically in the presence of Rashba spin-orbit coupling. We show that the spin-orbit interaction results in additional Raman transitions in the dot, whose amplitudes can be controlled externally by varying the spin-orbit coupling parameter. This novel effect can be used to tune Raman transitions in quantum dots. Alternatively, Raman spectroscopy can be used to observe how Rashba spin-orbit coupling manifests in few-electron quantum dots.

Spin interactions in a quantum dot containing a magnetic impurity

The electron and hole states in a CdTe quantum dot containing a single magnetic impurity in an external magnetic field are investigated using a multiband approximation which includes the heavy hole-light hole coupling effects. The electron-hole spin interactions and sp-d interactions between the electron, the hole and the magnetic impurity are also included. The exciton energy levels and optical transitions are evaluated using the exact diagonalization scheme. A novel mechanism is proposed here to manipulate impurity spin in the quantum dot which allows us to drive selectively the spin of the magnetic atom into each of its six possible orientations.

Interaction-driven distinctive electronic states of artificial atoms at the ZnO interface

We have investigated the electronic states of planar quantum dots at the ZnO interface containing a few interacting electrons in an externally applied magnetic field. The electron-electron interaction effects are expected to be much stronger in this case than in traditional semiconductor quantum systems, such as in GaAs or InAs quantum dots. In order to highlight that stronger Coulomb effects in the ZnO quantum dots, we have compared the energy spectra and the magnetization in this system to those of the InAs quantum dots. We have found that in the ZnO quantum dots the signatures of stronger Coulomb interaction manifests in an unique ground state that has very different properties than the corresponding ones in the InAs dot. Our results for the magnetization also exhibits behaviors never before observed in a quantum dot for a realistic set of parameters. We have found a stronger temperature dependence and other unexpected features, such as paramagnetic-like behavior at high temperatures for a quantum-dot helium.

Tuning of exciton states in a magnetic quantum ring

Abstract The exciton states in a CdTe quantum ring subjected to an external magnetic field containing a single magnetic impurity are investigated. We have used the multiband approximation which includes the heavy hole–light hole coupling effects. The electron–hole spin interactions and the s, p–d interactions between the electron, the hole and the magnetic impurity are also included. The exciton energy levels and optical transitions are evaluated using the exact diagonalization scheme. We show that due to the spin interactions it is possible to change the bright exciton state into the dark state and vice versa with the help of a magnetic field. We propose a new route to experimentally estimate the s, p–d spin interaction constants.

Spin-orbit interaction induced singlet-triplet resonant Raman transitions in quantum dot helium

From our theoretical studies of resonant Raman transitions in two-electron quantum dots (artificial helium atoms) we show that in this system, the singlet-triplet Raman transitions are allowed (in polarized configuration) only in the presence of spin-orbit interactions. With an increase of the applied magnetic field this transition dominates over the singlet-singlet and triplet-triplet transitions. This intriguing effect can therefore be utilized to tune Raman transitions as well as the spin-orbit coupling in few-electron quantum dots.

Interband transition in narrow gap InSb spherical layer quantum dot in the presence of electric field

We perform the theoretical investigation of interband dipole transitions in a narrow- gap InSb spherical layer quantum dot. We consider the transitions from the light hole and heavy hole states to the electron state of the conduction band. The dispersion law for electron and light hole is approximated using a two-band Kane model, while the heavy hole is described in the parabolic approximation. The effect of electric field on interband transitions is investigated.

Irregular Aharonov–Bohm effect for interacting electrons in a ZnO quantum ring

The electronic states and optical transitions of a ZnO quantum ring containing few interacting electrons in an applied magnetic field are found to be very different from those in a conventional semiconductor system, such as a GaAs ring. The strong Zeeman interaction and the Coulomb interaction of the ZnO system, two important characteristics of the electron system in ZnO, exert a profound influence on the electron states and on the optical properties of the ring. In particular, our results indicate that the Aharonov-Bohm (AB) effect in a ZnO quantum ring strongly depends on the electron number. In fact, for two electrons in the ZnO ring, the AB oscillations become aperiodic, while for three electrons (interacting) the AB oscillations completely disappear. Therefore, unlike in conventional quantum ring topology, here the AB effect (and the resulting persistent current) can be controlled by varying the electron number.