  Spin related phenomena in quantum nanostructures have attracted recently much
interest due to fast growing field of spintronics. In particular complex
nanostructures are important as they provide a versatile system to manipulate
spin and the electronic states. Such systems can be used as spin memory devices
or scalable quantum bits. We investigate the spin relaxation for an electron in
a complex structure composed of a quantum dot surrounded by a quantum ring. We
shown that modifications of the confinement potential result in the substantial
increase of the spin relaxation time.

Mesoscale and Nanoscale Physics