Electronic states in quantum dot atoms and molecules

We study electronic states in disk-shaped semiconductor artificial atoms and molecules containing just a few electrons. The few-electron ground states in the artificial atom show atomic-like properties such as a shell structure and obey Hund's rule. A magnetic field induces transitions in the ground states, which are identified as crossings between single particle states, singlet-triplet transitions and spin polarization. These properties are discussed in conjunction with exact calculation in which the effect of finite thickness of the disk is taken into account. An artificial molecule is made from vertically coupling two disk-shaped dots. When the two dots are quantum mechanically strongly coupled, the few-electron ground states are de-localized throughout the system and the electronic properties resemble those of a single artificial atom. (C) 1998 Elsevier Science B.V. All rights reserved.