Composite fermions and Landau-level mixing in the fractional quantum Hall effect.

The reduction of the energy gap due to Landau level mixing, characterized by the dimensionless parameter λ = (e/ǫl0)/h̄ωc, has been calculated by variational Monte Carlo for the fractional quantum Hall effect at filling fractions ν = 1/3 and 1/5 using a modified version of Jain’s composite fermion wave functions. These wave functions exploit the Landau level mixing already present in composite fermion wave functions by introducing a partial Landau level projection operator. Results for the energy gaps are consistent with experimental observations in n-type GaAs, but we conclude that Landau level mixing alone cannot account for the significantly smaller energy gaps observed in p-type systems. 73.40.Hm, 73.20.Dx