$\frac{5}{2}$ fractional quantum Hall state in GaAs with Landau level mixing

The Landau level mixing is the key in understanding the mysterious $5/2$ fractional quantum Hall effect in GaAs quantum well. Theoretical calculations with and without Landau level mixing show striking differences. However, the way to deal with the considerable strong Landau level mixing in GaAs is still unsatisfactory. We develop a method combining the screening and the perturbation theories to study the nature of the $5/2$ fractional quantum Hall effect in GaAs efficiently. The screening, which has been successful in explaining ZnO systems integrates out the low-energy Landau levels close to the related Landau level, while the other high-energy Landau levels are integrated out by the perturbation theory. We find that the ground states still hold the quasitriplet degeneracy, which implies the Pfaffian nature of the system. Furthermore, the particle-hole symmetry is only weakly violated since the particle-hole parity is close to unity. We propose that the ground state in the finite-size calculations could be approximated as a variational superposition of the Pfaffian and anit-Pfaffian states. In the experimental environment the symmetrized Pfaffian component is dominant, corresponding to a thermal conductance around 2.5 quanta that can be understood consequently.