Rapid Collapse of Spin Waves in Nonuniform Phases of the Second Landau Level

The spin degree of freedom in quantum phases of the second Landau level is probed by resonant light scattering. The long wavelength spin wave, which monitors the degree of spin polarization, is at the Zeeman energy in the fully spin-polarized state at nu = 3. At lower filling factors, the intensity of the Zeeman mode collapses, indicating loss of polarization. A novel continuum of low-lying excitations emerges that dominates near nu = 8/3 and nu = 5/2. Resonant Rayleigh scattering reveals that quantum fluids for nu < 3 break up into robust domain structures. While the state at nu = 5/2 is considered to be fully polarized, these results reveal unprecedented roles for spin degrees of freedom.