COMPOSITE-FERMION EXCITATIONS AND THE ELECTRONIC-SPECTRA OF FRACTIONAL QUANTUM HALL SYSTEMS

In the composite-fernion (CF) mean-field theory of a two-dimensional e lectron system, an electron Landau level whose filling factor is an od d denominator fraction can be transformed into an integral number of f illed CF Landau levels. This CF state corresponds to the ground state of a Laughlin incompressible liquid, with an energy gap equal to the ' 'effective'' CF cyclotron energy. Excited states are described by n(QE ) and n(QH), the number of quasielectron and quasihole CF excitations. The energies of individual quasielectrons or quasiholes and their ''F ermi liquid'' interactions can be investigated by comparing the CF pic ture with exact numerical results for a small number of electrons on a spherical surface.