Spin-singlet to spin-polarized phase transition at ν = 2 3: flux-trading in action

We analyze the phase transition between spin-singlet and spin-polarized states which occurs at ν = 2 3. The basic strategy is to use adiabatic flux-trading arguments to relate this transition to the analogous transition at ν = 2. The transition is found to be similar to a transition in ferromagnets. In our analysis, we find two possible scenarios. In one, the transition is first-order, in agreement with experimental and numerical studies of the ν = 2 3 transition. In the other, we find a second-order transition to a partially polarized state followed by a second-order transition to a fully polarized state. This picture is in qualitative agreement with experiments on the ν = 4 3 state, the particle-hole conjugate of ν = 2 3. We analyze the edge modes which propagate at the boundaries between regions of different phases and show that these do not support gapless excitations. Finally, we consider the possibility of a finite-temperature compressible state with a Fermi surface which would explain the non-zero ρ{variant}_xx seen in experiments.