Optical Studies of Quantum Phases with Filling Factors 2$\le \nu \le $3 in the Second Landau Level

We report low temperature inelastic light scattering and optical recombination measurements of quantum phases in the second Landau level of 2D electron systems. We focus on states with filling factors 2$\le \nu \le $3. An ultra high mobility, high density GaAs quantum well (240nm) is probed at low temperature (42mK -- 1.2K). Low energy spin excitations are studied by resonant inelastic light scattering. We confirm the existence of a ferromagnetic state at $\nu $ = 3 by the observation of a well-defined long wavelength spin wave mode at the Zeeman energy. Surprisingly, the ferromagnetic spin wave collapses at filling factors slightly away from $\nu $ = 3. While this behavior may be a signal of the disappearance of ferromagnetic order in the second Landau level, experiments in progress may offer deeper insights on fundamental interactions and quantum phases in the second Landau level.