Berlin 2024 – scientific programme
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O: Fachverband Oberflächenphysik
O 44: 2D Materials III: Electronic Structure (joint session O/TT)
O 44.2: Talk
Wednesday, March 20, 2024, 10:45–11:00, MA 005
Stacking-induced Chern insulator — Marwa Mannaï1,2, Jean-Noël Fuchs3, Frédéric Piéchon4, and •Sonia Haddad2,5 — 1Center for Quantum and Topological Systems, NYUAD Research Institute, New York University Abu Dhabi, UAE — 2Laboratoire de Physique de la Matière Condensée, Faculté des Sciences de Tunis, Université Tunis El Manar, Campus Universitaire 1060 Tunis, Tunisia — 3Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, LPTMC, 75005 Paris, France — 4Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France — 5Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
Graphene can be turned into a semimetal with broken time-reversal symmetry by adding a valley-dependent pseudoscalar potential that shifts the Dirac point energies in opposite directions, as in the modified Haldane model. We consider a bilayer obtained by stacking two time-reversed copies of the modified Haldane model, where conduction and valence bands cross to give rise to a nodal line in each valley. In the AB stacking, the interlayer hopping lifts the degeneracy of the nodal lines and induces a band repulsion, leading surprisingly to a chiral insulator with a Chern number C= pm 2. As a consequence, a pair of chiral edge states appears at the boundaries of a ribbon bilayer geometry. In contrast, the AA stacking does not show nontrivial topological phases. We discuss possible experimental implementations of our results. For more details: Phys. Rev. B 107, 045117 (2023)
Keywords: twisted bilayer graphene; superconductivity; Electron-phonon interaction