Dielectric mismatch effects in two-electron zero-dimensional nanosystems

Abstract

Two-electron Coulomb interaction and correlation effects in several spherically symmetric zero-dimensional semiconductor heterostructures are investigated in the large dielectric mismatch regime. Specifically, a semiconductor quantum dot (QD) embedded in air or a vacuum, an air-filled nanocavity in a semiconductor matrix, and a weakly confined ${D}^{\ensuremath{-}}$ center (two electrons bounded to a hydrogenic donor impurity in a QD embedded in air). A strong self-polarization-induced radial localization of the electronic density at the heterojunction interface yields surface states. In these states, the polarization of the electron-electron interaction strongly affects dynamics. For a low dielectric constant of the semiconductor building material, Wigner-like localization of the electronic density occurs. As we increase the dielectric constant, it is gradually suppressed. We prove that this gradual suppression is originated by the enhanced strength of the polarization potential accompanying the increase in permittivity. Additionally, in the presence of a weakly confined ${D}^{\ensuremath{-}}$ center in a QD, a transition phase from volume to surface states takes place. It is characterized, in a wide range of quantum dot radii, by a strong ground state reconstruction and a zero ${D}^{\ensuremath{-}}$ binding energy.