title: Crossover and coexistence of quasiparticle excitations in the fractional quantum hall regime at nu < or =1/3.
abstract: New low-lying excitations are observed by inelastic light scattering at filling factors nu=p/(phip+/-1) of the fractional quantum Hall regime with phi=4. Coexisting with these modes throughout the range nu < or =1/3 are phi=2 excitations seen at 1/3. Both phi=2 and phi=4 excitations have distinct behaviors with temperature and filling factor. The abrupt first appearance of the new modes in the low-energy excitation spectrum at nu > or near 1/3 suggests a marked change in the quantum ground state on crossing the phi=2-->phi=4 boundary at nu=1/3.
authors: Department of Physics, Columbia University, New York, NY 10027, USA.
authors: C F
authors: CF
authors: Hirjibehedin
authors: A
authors: A
authors: Pinczuk
authors: B S
authors: BS
authors: Dennis
authors: L N
authors: LN
authors: Pfeiffer
authors: K W
authors: KW
authors: West