2016/05/31 by Youngwook Kim, Patrick Herlinger, Pilkyung Moon +5 · 1 citation
Materials Science · Physics and Astronomy · #Bilayer graphene #Carbon Nanotubes in Composites #Charge (physics) #Condensed matter physics #Electron #Geology #Geometry #Graphene #Graphene research and applications #Inversion (geology) #Materials science #Phase transition #Physics #Quantum mechanics #Singularity #Topological Materials and Phenomena #Twist #Van Hove singularity #cond-mat.mes-hall #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1021/acs.nanolett.6b01906
published as Nano Lett., 16, 5053 (2016) · Nano Lett, ASAP
openalex publication_date 2016/07/07 · arxiv created 2016/07/12 · arxiv updated 2016/12/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
van Hove singularities (VHS's) in the density of states play an outstanding and diverse role for the electronic and thermodynamic properties of crystalline solids. At the critical point the Fermi surface connectivity changes, and topological properties undergo a transition. Opportunities to systematically pass a VHS at the turn of a voltage knob and study its diverse impact are however rare. With the advent of van der Waals heterostructures, control over the atomic registry of neighboring graphene layers offers an unprecedented tool to generate a low energy VHS easily accessible with conventional gating. Here we have addressed magnetotransport when the chemical potential crosses the twist angle induced VHS in twisted bilayer graphene. A topological phase transition is experimentally disclosed in the abrupt conversion of electrons to holes or vice versa, a loss of a nonzero Berry phase and distinct sequences of integer quantum Hall states above and below the singularity.