Spin transition in second Landau level

The fractional quantum Hall effect (FQHE) states in the second Landau level have attracted growing interests and intensive theoretical and experimental investigations due to them possibly being non-Abelian states. Recently, we systematically examined the spin polarization of the FQHE states in a series of high quality, low density two dimensional electron systems. Evidence of spin transition was observed, suggesting a more complicated nature of the FQHE ground states in the second Landau level.