Single- and few-particle states in core-shell nanowire quantum dots

Abstract

The electronic properties of single and few-particles in core-shell nanowire quantum dots (NWQD) are investigated. By performing configuration interaction (CI) calculations we particularly elucidate how elevated symmetry character (C3v or D2d) exhibited by single particle orbitals enhances the phase coherence of exciton-photon wavefunction though suppressing spin flip processes. Detailed calculations presented here demonstrate how strain-induced potentials manipulate the symmetry characters, intrinsic oscillator strength and electron-hole dipole in NWQDs. An orbital-dependent kinetic energy is defined based on single particle dispersion and orbital spreadout in k-space. It is shown the exchange occurring between this kinetic energy and strain-induced potentials is responsible for orbital distortions, and thus the energy reordering of different direct and correlation terms. Various structures have been examined to elaborate on the influence of size and orientation together with axial and lateral symmetry of NWQDs. Our many-body calculations suggest that binding energies of s-shell few particle resonances XX0 and trions are suppressed when axial and lateral localizations become comparable. Then exerting an external perturbation may renormalize the binding energies, realizing a transition from anti-binding to binding regime or reverse. In this regard, we specifically show that kinetic energy of single particles, and thus correlation energies of associated complexes, exposed to an electric field remain relatively unaffected and the interplay between direct Coulomb terms reorders the multiexcitonic resonances. Sub-micro-eV fine structure splitting along with the tunable XX0 binding energy offers NWQDs promising for generating entangled photons in both regular and time reordering schemes.