Theoretical approach to ground states of the ν=2/3 bilayer fractional quantum Hall systems

The ground states and phase diagrams of the ν=2/3 bilayer fractional quantum Hall systems at the layer balanced point are investigated theoretically by finite size exact-diagonalization calculations and an exactly solvable model. The degeneracy of the ground states occurs depending on the difference between intralayer and interlayer Coulomb energies, when interlayer tunneling energy (ΔSAS) gets close to zero. The transitions between the spin-polarized and spin-unpolarized phases are mainly determined by the competition between the Zeeman energy (ΔZ) and the electron Coulomb energy. The phase diagrams in ΔSAS–ΔZ planes are given for the first time. We also compare the numerical results with the experimental data and acquire a good agreement.