title: Particle-hole symmetry and the Pfaffian state.
abstract: We show that the particle-hole conjugate of the Pfaffian state-or "anti-Pfaffian" state-is in a different universality class from the Pfaffian state, with different topological order. The two states can be distinguished easily by their edge physics: their edges differ in both their thermal Hall conductance and their tunneling exponents. At the same time, the two states are exactly degenerate in energy for a nu=5/2 quantum Hall system in the idealized limit of zero Landau level mixing. Thus, both are good candidates for the observed sigma_{xy}=5/2(e;{2}/h) quantum Hall plateau.
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Levin
authors.forename: Bertrand I
authors.initials: BI
authors.lastname: Halperin
authors.forename: Bernd
authors.initials: B
authors.lastname: Rosenow