Spin-reversed Quasiparticles in the Fractional Quantum Hall Effect - Finite System Calculations

The elementary charged excitations at 1/3 Landau level filling have been studied for various spin polarizations for finite electron systems in a periodic rectangular geometry. In the absence of Zeeman energy, the spin-reversed excitations, studied for three to six electron systems show significant reduction of the energy gap, compared to the fully spin-polarized quasiparticle-quasihole gap, studied for upto seven electron systems. In the presence of Zeeman energy, the lowest energy excitations involve spin-reversed quasiparticles and spin-polarized quasiholes for low magnetic fields. With increasing magnetic fields, a crossover point is reached (in the region B < 10 T), beyond which a fully spin polarized quasiparticle-quasihole state will be energetically favored. The Zeeman energy due to spin-flip explains qualitatively the linear magnetic field dependence of the activation energies observed experimentally.