Low energy spectra of isotropic quantum dots are calculated in the regime of low electron densities where Coulomb interaction causes strong correlations. The earlier developed pocket state method is generalized to allow for continuous rotations. Detailed predictions are made for dots of shallow confinements and small particle numbers, including the occurance of spin blockades in transport.

We theoretically investigated excitonic states, energy and oscillator strength of optical transitions in GaN quantum dots characterized by different size, shape, interface, and substrate. On the basis of our multi-band model we determined that the piezoelectric field-induced red shift of the ground state transition, observed in recent experiments, can manifest itself only in strained GaN/AIN do...

The optical properties of graphene quantum dots (GQDs) were investigated theoretically. We focused on the photoinduced charge transfer and electron-hole coherence of single-layer graphene in the electronic transitions in the visible regions. Surface functionalization with donor or acceptor groups produced a red shift in the absorption spectrum, and electrons and holes were highly delocalized. T...

In this September issue, we bring you very diverse, but interesting, papers. South African authors have written for us about the quality of rapid HIV testing and testers’ compliance.1 They found sub-standard practices in relation to testing – a matter of concern. Nigerian authors on the other hand report adverse outcomes of TB-HIV patients at PEPFAR/DOTS centres2, while Ethiopian authors have s...

This paper reports a study of photooxidation and photomodification processes of the CdTe/CdS quantum dots embedded in a polymer matrix under ambient condition. During the first few minutes of irradiation, the quasi-inverse increase in photoluminescence intensity has been observed indicating the passivation of the nanocrystal surface traps by water molecules. A prolonged irradiation of the polym...

We present an alternative to the Kohn-Sham formulation of density-functional theory for the ground-state properties of strongly interacting electronic systems. The idea is to start from the limit of zero kinetic energy and systematically expand the universal energy functional of the density in powers of a "coupling constant" that controls the magnitude of the kinetic energy. The problem of mini...

The complicated behaviors of InAs/GaAs quantum dots with increasing V/III ratio associated with several competing mechanisms have been described. The results demonstrate that the densities of InAs quantum dots can be tuned in a wide range from 105 to 1010 cm-2 by simply manipulating V/III ratio via metal-organic chemical vapor deposition. These results are mainly ascribed to the changes of cove...

We propose an efficient control protocol for charge transfer in a double quantum dot. We consider numerically a two-dimensional model system, where the quantum dots are subjected to time-dependent electric fields corresponding to experimental gate voltages. Our protocol enables navigation in the charge stability diagram from a state to another through controllable variation of the fields. We sh...

Quantum dots (QDs) are among the most promising items in the nanomedicine toolbox. These nanocrystal fluorophores have several potential medical applications including nanodiagnostics, imaging, targeted drug delivery, and photodynamic therapy. The diverse potential applications of QDs are attributed to their unique optical properties including broad-range excitation, size-tunable narrow emissio...

A method to determine the effects of the geometry and lateral ordering on the electronic properties of an array of one-dimensional self-assembled quantum dots is discussed. A model that takes into account the valence-band anisotropic effective masses and strain effects must be used to describe the behavior of the photoluminescence emission, proposed as a clean tool for the characterization of d...