Journal Article

Manifestation of unconventional biexciton states in quantum dots

Kako, Satoshi, Kalinowski, Stefan, Hönig, Gerald, Bimberg, Dieter, Schliwa, Andrei, Callsen, Gordon, Arakawa, Yasuhiko, Hoffmann, Axel, Kindel, Christian

2014

Overview

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. Artificial atoms usually constitute an orbital structure for trapped charge carriers. Here, Hönig et al . demonstrate that polarization fields and large charge carrier masses can dilute the common orbital conception and find a hybrid-biexciton molecule that enables anomalous spin configurations.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 140/125 / 639/624/399/1017 / 639/766/119 / Decay / Humanities and Social Sciences / multidisciplinary / Science / Science (multidisciplinary)