title: Evidence of Landau levels and interactions in low-lying excitations of composite fermions at 1/3<or= nu <or=2/5.
abstract: Excitation modes in the range 2/5>or=nu>or=1/3 of the fractional quantum Hall regime are observed by resonant inelastic light scattering. Spectra of spin-reversed excitations suggest a structure of lowest spin-split Landau levels of composite fermions that is similar to that of electrons. Spin-flip energies determined from spectra reveal significant composite fermion interactions. The filling factor dependence of mode energies displays an abrupt change in the middle of the range when there is partial population of a composite fermion level.
authors.affiliation: Department of Applied Physics and Applied Math, Columbia University, New York, New York 10027, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: Dujovne
authors.forename: A
authors.initials: A
authors.lastname: Pinczuk
authors.forename: Moonsoo
authors.initials: M
authors.lastname: Kang
authors.forename: B S
authors.initials: BS
authors.lastname: Dennis
authors.forename: L N
authors.initials: LN
authors.lastname: Pfeiffer
authors.forename: K W
authors.initials: KW
authors.lastname: West