Spin excitations in the fractional quantum Hall regime at v less than or similar to 1/3

We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors v less than or similar to 1/3. A spin mode is observed below the Zeeman energy. The filling factor dependence of the mode energy is consistent with its assignment to spin flip excitations of composite fermions (CF) with four attached flux quanta (phi = 4). Our findings reveal a CF Landau level structure in the 0 = 4 sequence. (c) 2006 Published by Elsevier B.V.