Landau level mixing in the nu=5/2 fractional quantum Hall state

The nu=5/2 fractional quantum Hall state is studied numerically, directly including the effects of electron scattering between neighboring Landau levels. Significant reduction of the excitation gap caused by the LL mixing explains the discrepancy between earlier calculations and experiments. On the other hand, LL mixing also considerably reduces overlaps with the Moore--Read wavefunction, raising a question of the actual realization of nonabelian quasiparticles in present experiments.