Fractional quantum Hall effect in tilted magnetic fields

The quasiparticle-quasihole energy gap in the fractional quantum Hall effect has been studied in the case of a tilted magnetic field, using the standard procedure of finite-size calculations in a periodic rectangular geometry. We found that the effect of the tilted field is to influence the wave function perpendicular to the two-dimensional electron plane to a certain extent. The breaking of the electron-hole symmetry, as observed in the experiments, however, cannot be explained in this approach without invoking the spin reversal in the ground state.