  The electronic properties of quasi two-dimensional multicomponent systems are
investigated in the presence of a perpendicular magnetic field. The effects of
the presence of a few valence band holes on the properties of quantum Hall
systems are examined by analyzing the results of exact numerical
diagonalization of small electron-hole systems confined to the spherical
surface. The novel type of elementary excitations, the angular momenta, binding
energies, interaction pseudopotentials, and effects on the photoluminescence
spectrum are presented.
