Tilted magnetic field effect on a double-layer quantum Hall system

The effect of a parallel magnetic field on the quantum Hall state of a double-layer system at total filling factor {ν}=(4n+1), with n being the Landau-level index, is studied. While our result is consistent with previous ones, which indicate that the system at {ν}=1 undergoes a parallel-magnetic-field-induced phase transition, we find that the phase transition also takes place at higher filling factors. For a certain parameter range, we observe an instability of the quantum Hall state towards probably a charge-density-wave state at a smaller parallel magnetic field before the phase transition takes place.