Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 44: Twisted Materials / Systems
TT 44.2: Vortrag
Mittwoch, 20. März 2024, 11:45–12:00, H 3007
Dynamical correlations and order in magic-angle twisted bilayer graphene — •Gautam Rai1, Lorenzo Crippa2, Dumitru Călugăru3, Haoyu Hu4, Luca de' Medici5, Antoine Georges6, 7, 8, 9, B. Andrei Bernevig3, 4, 10, Roser Valentí11, Giorgio Sangiovanni2, and Tim Wehling1, 12 — 1U Hamburg — 2U Würzburg — 3Princeton U — 4DIPC, Donostia-San Sebastian — 5ESPCI, Paris — 6Collège de France, Paris — 7Flatiron Institute, New York — 8École Polytechnique, Palaiseau Cedex — 9Université de Genève — 10IKERBASQUE, Bilbao — 11Goethe U Frankfurt — 12Hamburg CUI
In magic-angle twisted bilayer graphene, transport, thermodynamic and spectroscopic experiments pinpoint at a competition between distinct low-energy states with and without electronic order. We use Dynamical Mean Field Theory (DMFT) to study the emergence of electronic correlations and long-range order without strain. We explain the nature of emergent insulating and correlated metallic states by three central phenomena: (i) the formation of local spin and valley isospin moments around 100K, (ii) the ordering of these moments around 10K, and (iii) a cascadic redistribution of charge between localized and delocalized electronic states upon doping. Depending on the presence (absence) of order, we find insulating gaps (spectral weight depletion) at integer fillings, and a good (bad) metal at fractional fillings. Our findings provide a unified understanding of the most puzzling aspects of STS and transport experiments, including the isospin Pomeranchuk effect and doping-induced compressibility cascades.
Keywords: Twisted bilayer graphene; Magic angle; Correlated electrons; Spontaneous symmetry-breaking; Dynamical mean field theory