Dynamical correlations and order in magic-angle twisted bilayer graphene

  • 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, as well as a competition between localized and delocalized charge carriers. In this study, we utilize Dynamical Mean Field Theory (DMFT) on the topological heavy Fermion (THF) model of twisted bilayer graphene to investigate the emergence of electronic correlations and long-range order in the absence of strain. We explain the nature of emergent insulating and correlated metallic states, as well as transitions between them driven by three central phenomena: (i) the formation of local spin and valley isospin moments around 100K, (ii) the ordering of the local isospin moments around 10K, and (iii) a cascadic redistribution of charge between localized and delocalized electronic states upon doping. At integer fillings, we find that low energy spectral weight is depleted in the symmetric phase, while we find insulating states with gaps enhanced by exchange coupling in the zero-strain ordered phases. Doping away from integer filling results in distinct metallic states: a "bad metal" above the ordering temperature, where coherence of the low-energy electronic excitations is suppressed by scattering off the disordered local moments, and a "good metal" in the ordered states with coherence of quasiparticles facilitated by isospin order. Upon doping, there is charge transfer between the localized and delocalized orbitals of the THF model such that they get periodically filled and emptied in between integer fillings. This charge reshuffling manifests itself in cascades of doping-induced Lifshitz transitions, local spectral weight redistributions and periodic variations of the electronic compressibility ranging from nearly incompressible to negative.

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Metadaten
Author:Gautam RaiORCiD, Lorenzo CrippaORCiD, Dumitru CălugăruORCiD, Haoyu HuORCiD, Luca de' MediciORCiD, Antoine GeorgesORCiD, B. Andrei BernevigORCiDGND, Roser ValentíORCiDGND, Giorgio SangiovanniORCiDGND, Tim O. WehlingORCiDGND
URN:urn:nbn:de:hebis:30:3-824407
URL:https://arxiv.org/abs/2309.08529v1
DOI:https://doi.org/10.48550/arXiv.2309.08529
ArXiv Id:http://arxiv.org/abs/2309.08529v1
Parent Title (English):arXiv
Publisher:arXiv
Document Type:Preprint
Language:English
Date of Publication (online):2023/09/15
Date of first Publication:2023/09/15
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2024/02/20
Issue:2309.08529 Version 1
Edition:Version 1
Page Number:38
HeBIS-PPN:516154699
Institutes:Physik / Physik
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 4.0