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Graphene is one of the most versatile materials to realize exotic phenomena in condensed matter, as a consequence of the emergent Dirac dispersion at low energies. Introducing one more layer of complexity, we find bilayer graphene, which can be manipulated to achieve an arbitrary twist angle between the two layers. Twisted bilayer graphene (TBG) has recently attracted a lot of attention for the observed superconductivity and correlated electronic behavior at particular twist angles called magic angles. Here, I discuss two novel ways to control the electronic properties of twisted bilayer graphene, in particular: - Artificial gauge fields: We established that the application of a homogeneous electric field perpendicular to the bilayer is mathematically equivalent to a new kind of synthetic gauge field in the small twist angle regime. This identification opens the door for the generation and detection of pseudo-Landau levels in graphene platforms within robust setups, which do not depend on strain engineering. Furthermore, this new artificial gauge field leads to the development of highly localized modes in emergent triangular or Kagome lattices, associated with flat bands close to charge neutrality. - Triple point Fermions: These are elusive electronic excitations that generalize Dirac and Weyl modes beyond the conventional high energy paradigm. Yet, finding real materials naturally hosting these excitations at the Fermi energy has remained a challenge. In this work, we show how TBG can realize robust triple point fermions in two dimensions by the introduction of localized impurities.

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Aline Ramires, ICTP, Sao Paulo, Brazil
Seminar Room 0.03, ETP
Contact: Sebastian Diehl