title: Manifestation of unconventional biexciton states in quantum dots.
abstract: Although semiconductor excitons consist of a fermionic subsystem (electron and hole), they carry an integer net spin similar to Cooper-electron-pairs. While the latter cause superconductivity by forming a Bose-Einstein-condensate, excitonic condensation is impeded by, for example, a fast radiative decay of the electron-hole pairs. Here, we investigate the behaviour of two electron-hole pairs in a quantum dot with wurtzite crystal structure evoking a charge carrier separation on the basis of large spontaneous and piezoelectric polarizations, thus reducing carrier overlap and consequently decay probabilities. As a direct consequence, we find a hybrid-biexciton complex with a water molecule-like charge distribution enabling anomalous spin configurations. In contrast to the conventional-biexciton complex with a net spin of s=0, the hybrid-biexciton exhibits s=±3, leading to completely different photoluminescence signatures in addition to drastically enhanced charge carrier-binding energies. Consequently, the biexcitonic cascade via the dark exciton can be enhanced on the rise of temperature as approved by photon cross-correlation measurements.
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Hönig
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Gordon
authors.initials: G
authors.lastname: Callsen
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Andrei
authors.initials: A
authors.lastname: Schliwa
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kalinowski
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kindel
authors.affiliation: Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo 153-8904, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kako
authors.affiliation: Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo 153-8904, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Arakawa
authors.affiliation: 1] Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany [2] King-Abdulaziz-University, 21589 Jeddah, Kingdom of Saudi Arabia.
authors.forename: Dieter
authors.initials: D
authors.lastname: Bimberg
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Hoffmann