We report on fixed phase diffusion Monte Carlo calculations that show that, even for a large amount of Landau level mixing, the energies of the Pfaffian and anti-Pfaffian phases remain very nearly the same, as also do the excitation gaps at 1/3 and 2/3. These results, combined with previous theoretical and experimental investigations, indicate that particle hole (PH) symmetry for composite fermion states is much more robust than a priori expected, emerging even in models that explicitly break PH symmetry. We provide insight into this fact by showing that the low energy physics of a generic repulsive 3-body interaction is captured, to a large extent and over a range of filling factors, by a mean field approximation that maps it into a PH symmetric 2-body interaction. This explains why Landau level mixing, which effectively generates such a generic 3-body interaction, is inefficient in breaking PH symmetry. As a byproduct, our results provide a systematic construction of a 2-body interaction which produces, to a good approximation, the Pfaffian wave function as its ground state.
I. BACKGROUND AND MOTIVATIONIt has been appreciated since the early 1980s that Landau level (LL) mixing leads to corrections in various observable quantities in fractional quantum Hall effect (FQHE), such as the transport gaps 1,2 . The effect of LL mixing is two-fold: it alters the 2-body interaction and also induces multi-particle interaction. While both lead to corrections, the latter also breaks the symmetry under particle-hole (PH) transformation, which is an exact symmetry for electrons confined to a single LL and interacting by a 2-body interaction, providing an exact relation between the wave functions and spectra at filling factors ν and 1 − ν.The issue of PH symmetry has received much attention in recent years, in the contexts of both the competition of the Moore-Read Pfaffian 3 (Pf) and the antiPfaffian 4,5 (APf) states for the ν = 5/2 FQHE 6-12 , and the composite-fermion (CF) Fermi sea at ν = 1/2 13-18 . A surprising message revealed by these studies is that the PH symmetry for CF liquids is much more robust than one might a priori anticipate, emerging even for Hamiltonians that explicitly break PH symmetry. Let us list some examples. (i) The most dominant PH symmetry breaking term induced by LL mixing is the 3-body interaction 6 . Ref.19 found, surprisingly, that even a pure 3-body interaction produces, for a broad range of parameters, the standard Jain CF states at ν = n/(2n±1) 20,21 , which satisfy PH symmetry to a very good approximation; this demonstrates an emergent PH symmetry in the ground state for a model Hamiltonian that explicitly breaks PH symmetry. (ii) An emergent PH symmetry was found also for spinful bosons in the lowest LL (LLL) interacting via the hard core interaction 22 ; a priori, a bosonic system is not expected to obey PH symmetry at all. (iii) Wang et al. 18 have demonstrated that the Halperin-Lee-Read theory of composite fermions produces results that are consistent with PH symmetry, even though the ...