title: Particle-hole symmetry and the nu=5/2 quantum Hall state.
abstract: We discuss the implications of approximate particle-hole symmetry in a half-filled Landau level in which a paired quantum Hall state forms. We note that the Pfaffian state is not particle-hole symmetric. Therefore, in the limit of vanishing Landau-level mixing, in which particle-hole transformation is an exact symmetry, the Pfaffian spontaneously breaks this symmetry. There is a particle-hole conjugate state, which we call the anti-Pfaffian, which is degenerate with the Pfaffian in this limit. We observe that strong Landau-level mixing should favor the Pfaffian, but it is an open problem which state is favored for the moderate Landau-level mixing which is present in experiments. We discuss the bulk and edge physics of the anti-Pfaffian. We analyze a simplified model in which transitions between analogs of the two states can be studied in detail. Finally, we discuss experimental implications.
authors.affiliation: Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030, USA.
authors.forename: Sung-Sik
authors.initials: SS
authors.lastname: Lee
authors.forename: Shinsei
authors.initials: S
authors.lastname: Ryu
authors.forename: Chetan
authors.initials: C
authors.lastname: Nayak
authors.forename: Matthew P A
authors.initials: MP
authors.lastname: Fisher