5 - Quantum Dots of Diluted Magnetic Semiconductor Compounds

Abstract

In this chapter quantum many body theoretical methods have been used to study the electronic structure and magnetic properties of GaAs - and InAs - based, small quantum dots (QDs) doped with manganese or vanadium atoms. Interest to such systems has grown since experimental synthesis of nanoscale magnetic semiconductors, that is, nanoscale semiconductor compounds with enhanced magnetic properties. Such enhancement is achieved by several methods and in particular, by doping common semiconductor compounds with Mn or V atoms. Experimental studies indicate that electronic charge in the case of thin nanoscale “diluted magnetic” semiconductor films and QDs is delocalized in the vicinity of the dopant atoms. As described in this chapter quantum many body theory-based, computational synthesis (i.e., virtual synthesis) of tetrahedral symmetry GaAs and InAs small pyramidal QDs doped with substitution Mn or V atoms confirms the above experimental findings. Electron charge re-distribution in response to permutations induced by dopant atoms with 3d electrons provides a physical mechanism responsible for magnetization and stabilization of such nanoscale magnetic semiconductor QDs, and leads to the development of what can be described as delocalized, spin-polarized regions of the electron charge deficit (“holes”). In some of such nanoscale molecular magnets numerical values of the electron spin density distribution (SDD) are relatively large, indicating that such QD systems may be used as nanomaterials for spintronics, magneto-optical sensor and quantum information processing applications.