Phase diagram of the v = 5/2 fractional quantum Hall effect: Effects of Landau-level mixing and nonzero width. Pakrouski, K., Peterson, M., M., R., Jolicoeur, T., Scarola, V., W., Nayak, C., & Troyer, M. Physical Review X, 5(2):021004, 4, 2015.
Phase diagram of the v = 5/2 fractional quantum Hall effect: Effects of Landau-level mixing and nonzero width [pdf]Paper  Phase diagram of the v = 5/2 fractional quantum Hall effect: Effects of Landau-level mixing and nonzero width [link]Website  doi  abstract   bibtex   
Interesting non-Abelian states, e.g., the Moore-Read Pfaffian and the anti-Pfaffian, offer candidate descriptions of the v = 5/2 fractional quantum Hall state. But, the significant controversy surrounding the nature of the v = 5/2 state has been hampered by the fact that the competition between these and other states is affected by small parameter changes. To study the phase diagram of the v = 5/2 state, we numerically diagonalize a comprehensive effective Hamiltonian describing the fractional quantum Hall effect of electrons under realistic conditions in GaAs semiconductors. The effective Hamiltonian takes Landau-level mixing into account to lowest order perturbatively in ?, the ratio of the Coulomb energy scale to the cyclotron gap. We also incorporate the nonzero width w of the quantum-well and subband mixing. We find the ground state in both the torus and spherical geometries as a function of ? and w. To sort out the nontrivial competition between candidate ground states, we analyze the following four criteria: its overlap with trial wave functions, the magnitude of energy gaps, the sign of the expectation value of an order parameter for particle-hole symmetry breaking, and the entanglement spectrum. We conclude that the ground state is in the universality class of the Moore-Read Pfaffian state, rather than the anti-Pfaffian, for ? < ?c(w), where ?c(w) is a w-dependent critical value 0.6 ? ?c(w) ? 1. We observe that both Landau-level mixing and nonzero width suppress the excitation gap, but Landau-level mixing has a larger effect in this regard. Our findings have important implications for the identification of non-Abelian fractional quantum Hall states.

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