Wigner molecule on the top of a quantum dot

Quantum dots in GaAs heterostructures display a complex inner structure in a large magnetic field. The distribution of electrons over different Landau levels results in the formation of alternating compressible and incompressible regions. We investigate theoretically the situation when only a few electrons are confined to the uppermost Landau level. We show that these extra electrons form a Wigner molecule. The magnetic field controls the number of electrons in the molecule, and this creates the possibility of manipulating few-electron objects. Moreover, in this way one can manipulate fractional charges. We discuss briefly the stability of the molecule in the presence of a fluctuating donor potential and the slow charge dynamics, which is intrinsic for the system under consideration.