The half-filled Landau level – composite fermions and dipoles

The composite-fermion approach as formulated in the Fermion Chern-Simons theory has been very successful in describing the physics of the lowest Landau level near Landau level filling factor ν = 1/2. Recent work has emphasized the fact that the true low energy quasiparticles at this filling factors are electrically neutral and carry an electric dipole moment. In a previous work, we discussed at length two formulations in terms of dipolar quasiparticles. Here we briefly review one approach – termed electron-centered quasiparticles – and show how it can be extended from ν = 1/2 to nearby filling factors ν where the low-energy quasiparticles carry both an electric dipole moment and an overall charge e = (2ν − 1)e.