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TT: Fachverband Tiefe Temperaturen

TT 46: Poster Session: Frustrated Magnets, Quantum Magnets, Charge Order and Complex Oxids

TT 46.5: Poster

Mittwoch, 18. März 2020, 15:00–19:00, P2/2OG

Emergence and stability of spin-valley entangled quantum liquids in Moiré heterostructures — •Dominik Kiese, Finn Lasse Buessen, Ciaran Hickey, Simon Trebst, and Michael M. Scherer — Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany

Moiré heterostructures with nearly flat bands have recently been established as a new playground for strongly-correlated electron physics. The precise nature of the correlated states is yet to be understood through the application of quantum many-body methods. Essential traits of phenomenological models for Moiré heterostructures include a hexagonal superlattice, a two-valley structure, as well as extended Hubbard and Hund's interaction terms. Taking a strong-coupling perspective, these features result in generalized Heisenberg models with separate spin and valley degrees of freedom. Here, the combination of geometric frustration and enhanced quantum fluctuations may inhibit the formation of conventional magnetic order. We study such extended spin-valley Heisenberg models using functional RG methods and find rich phase diagrams exhibiting stable realms of quantum spin-valley liquid behavior. We further show that even for purely antiferromagnetic couplings, ferromagnetic order may emerge in an extensive parameter regime. We discuss the relevance of our results for trilayer graphene on hexagonal boron nitride and twisted double bilayer graphene.