arXiv subjects

Weiwei Zhang

Publications and source records attributed to Weiwei Zhang.

111 records · Page 7Linked to original sources

arXiv2010

Atomistic pseudopotential calculations of the optical properties of InAs/InP self-assembled quantum dots

We present a comprehensive study of the optical properties of InAs/InP self-assembled quantum dots (QDs) using an empirical pseudopotential method and configuration interaction treatment of the many-particle effects. The results are compared to those of InAs/GaAs QDs. The main results are: (i) The alignment of emission lines of neutral exciton, charged exciton and biexciton in InAs/InP QDs is quite different from that in InAs/GaAs QDs. (ii) The hidden correlation in InAs/InP QDs is 0.7 - 0.9 meV, smaller than that in InAs/GaAs QDs. (iii) The radiative lifetimes of neutral exciton, charged exciton and biexciton in InAs/InP QDs are about twice longer than those in InAs/GaAs QDs. (v) The phase diagrams of few electrons and holes in InAs/InP QDs differ greatly from those in InAs/GaAs QDs. The filling orders of electrons and holes are shown to obey the Hund's rule and Aufbau principle, and therefore the photoluminescence spectra of highly charged excitons are very different from those of InAs/GaAs QDs.

cond-mat.mtrl-sci↗

arXiv2008

Hidden correlations of exciton complexes in self-assembled quantum dots and rings

The binding energies of trions ($X^+$, $X^-$) and biexciton (XX) in self-assembled semiconductor quantum dots (QDs) are very sensitive to the geometry and chemical composition of the QDs, and are random from dots to dots. However, in this letter, we show through analytical and numerical methods that the transition energies of the exciton complexes in self-assembled quantum dots and rings follow a simple and robust rule, i.e., the sum of exciton and biexciton transition energies minus the transition energies of trions is always positive and almost a constant for the same type of quantum dots and rings as a consequence of a pure Coulomb correlation effect. More interestingly, this quantity show a sharp transition when the topology change from a dot to a ring. This {\it hidden} correlation effect, directly measurable in experiments, offers a useful way to understand the photoluminescence spectra of self-assembled quantum dots and rings.

cond-mat.mtrl-sci↗

arXiv2008

Giant optical anisotropy in cylindrical self-assembled InAs/GaAs quantum rings

Using a single-particle atomistic pseudopotential method followed by a many-particle configuration interaction method, we investigate the geometry, electronic structure and optical transitions of a self-assembled InAs/GaAs quantum ring (QR), changing its shape continously from a lens-shaped quantum dot (QD) to a nearly one dimensional ring. We find that the biaxial strain in the ring is strongly asymmetric in the plane perpendicular to the QR growth direction, leading to giant optical anisotropy.

cond-mat.mtrl-sci↗