title: Broken-Symmetry Quantum Hall States in Twisted Bilayer Graphene.
abstract: Twisted bilayer graphene offers a unique bilayer two-dimensional-electron system where the layer separation is only in sub-nanometer scale. Unlike Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin and valley, providing eight-fold degeneracy in the low energy states. We have investigated broken-symmetry quantum Hall (QH) states and their transitions due to the interplay of the relative strength of valley, spin and layer polarizations in twisted bilayer graphene. The energy gaps of the broken-symmetry QH states show an electron-hole asymmetric behaviour, and their dependence on the induced displacement field are opposite between even and odd filling factor states. These results strongly suggest that the QH states with broken valley and spin symmetries for individual layer become hybridized via interlayer tunnelling, and the hierarchy of the QH states is sensitive to both magnetic field and displacement field due to charge imbalance between layers.
authors.affiliation: Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea.
authors.forename: Youngwook
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.
authors.forename: Jaesung
authors.initials: J
authors.lastname: Park
authors.affiliation: Center for Artificial Low Dimensional Electronic System, Institute for Basic Science (IBS), Pohang 37673, Korea.|Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Korea.
authors.forename: Intek
authors.initials: I
authors.lastname: Song
authors.affiliation: Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea.
authors.forename: Jong Mok
authors.initials: JM
authors.lastname: Ok
authors.affiliation: Department of Physics, Kyungpook National University, Daegu 702-701, Korea.
authors.forename: Younjung
authors.initials: Y
authors.lastname: Jo
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniquchi
authors.affiliation: Center for Artificial Low Dimensional Electronic System, Institute for Basic Science (IBS), Pohang 37673, Korea.|Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Korea.
authors.forename: Hee Cheul
authors.initials: HC
authors.lastname: Choi
authors.affiliation: Applied Quantum Composites Research Center, KIST Jeonbuk Institute of Advanced Composite Materials, Jeonbuk 55324, Korea.
authors.forename: Dong Su
authors.initials: DS
authors.lastname: Lee
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.
authors.forename: Suyong
authors.initials: S
authors.lastname: Jung
authors.affiliation: Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea.
authors.forename: Jun Sung
authors.initials: JS
authors.lastname: Kim