title: Robust fractional quantum Hall effect in the N=2 Landau level in bilayer graphene.
abstract: The fractional quantum Hall effect is a canonical example of electron-electron interactions producing new ground states in many-body systems. Most fractional quantum Hall studies have focussed on the lowest Landau level, whose fractional states are successfully explained by the composite fermion model. In the widely studied GaAs-based system, the composite fermion picture is thought to become unstable for the N≥2 Landau level, where competing many-body phases have been observed. Here we report magneto-resistance measurements of fractional quantum Hall states in the N=2 Landau level (filling factors 4<|ν|<8) in bilayer graphene. In contrast with recent observations of particle-hole asymmetry in the N=0/N=1 Landau levels of bilayer graphene, the fractional quantum Hall states we observe in the N=2 Landau level obey particle-hole symmetry within the fully symmetry-broken Landau level. Possible alternative ground states other than the composite fermions are discussed.
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Georgi
authors.initials: G
authors.lastname: Diankov
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.|Department of Physics, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Chi-Te
authors.initials: CT
authors.lastname: Liang
authors.affiliation: Department of Physics, Duke University, Durham, North Carolina 27708, USA.|Department of Physics and Astronomy, Appalachian State University, Boone, North Carolina 28608, USA.
authors.forename: François
authors.initials: F
authors.lastname: Amet
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gallagher
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Menyoung
authors.identifier: http://orcid.org/0000-0003-1954-3198
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Bestwick
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Tharratt
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA.
authors.forename: William
authors.initials: W
authors.lastname: Coniglio
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA.
authors.forename: Jan
authors.initials: J
authors.lastname: Jaroszynski
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305, Japan.
authors.forename: Kenji
authors.identifier: http://orcid.org/0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: David
authors.initials: D
authors.lastname: Goldhaber-Gordon