title: Anomalous sequence of quantum Hall liquids revealing a tunable Lifshitz transition in bilayer graphene.
abstract: Bilayer graphene is a unique system where both the Fermi energy and the low-energy electron dispersion can be tuned. This is brought about by an interplay between trigonal warping and the band gap opened by a transverse electric field. Here, we drive the Lifshitz transition in bilayer graphene to experimentally controllable carrier densities by applying a large transverse electric field to a h-BN-encapsulated bilayer graphene structure. We perform magnetotransport measurements and investigate the different degeneracies in the Landau level spectrum. At low magnetic fields, the observation of filling factors -3 and -6 quantum Hall states reflects the existence of three maxima at the top of the valence-band dispersion. At high magnetic fields, all integer quantum Hall states are observed, indicating that deeper in the valence band the constant energy contours are singly connected. The fact that we observe ferromagnetic quantum Hall states at odd-integer filling factors testifies to the high quality of our sample. This enables us to identify several phase transitions between correlated quantum Hall states at intermediate magnetic fields, in agreement with the calculated evolution of the Landau level spectrum. The observed evolution of the degeneracies, therefore, reveals the presence of a Lifshitz transition in our system.
authors.affiliation: Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Varlet
authors.affiliation: Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Dominik
authors.initials: D
authors.lastname: Bischoff
authors.affiliation: Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Pauline
authors.initials: P
authors.lastname: Simonet
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ihn
authors.affiliation: Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Klaus
authors.initials: K
authors.lastname: Ensslin
authors.affiliation: Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.
authors.forename: Marcin
authors.initials: M
authors.lastname: Mucha-Kruczyński
authors.affiliation: Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom.
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Fal'ko