Lattice Collective Modes from a Continuum Model of Magic-Angle Twisted Bilayer Graphene

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dc.creatorKumar, Ajesh
dc.creatorXie, Ming
dc.creatorMacDonald, Allan H.
dc.date.accessioned2024-02-02T14:16:12Z
dc.date.available2024-02-02T14:16:12Z
dc.date.issued2021-07-08
dc.description.abstractWe show that the insulating states of magic-angle twisted bilayer graphene support a series of collective modes corresponding to local particle-hole excitations on triangular lattice sites. Our theory is based on a continuum model of the magic angle flat bands. When the system is insulating at moir´e band filling ν = −3, our calculations show that the ground state supports seven low-energy modes that lie well below the charge gap throughout the moir´e Brillouin zone, one of which couples strongly to THz photons. The low-energy collective modes are faithfully described by a model with a local SU(8) degree of freedom in each moir´e unit cell that we identify as the direct product of spin, valley, and an orbital pseudospin. Apart from spin and valley-wave modes, the collective mode spectrum includes a low-energy intra-flavor exciton mode associated with transitions between flat valence and conduction band orbitals.
dc.description.departmentCenter for Dynamics and Control of Materials
dc.description.sponsorshipAK was supported by the National Science Foundation through the Center for Dynamics and Control of Materials: an NSF MRSEC under Cooperative Agreement No. DMR- 1720595. MX and AHM were supported by DOE BES grant DE- FG02-02ER45958.
dc.identifier.doihttps://doi.org/10.48550/arXiv.2010.05946
dc.identifier.urihttps://hdl.handle.net/2152/123568
dc.identifier.urihttps://doi.org/10.26153/tsw/50363
dc.language.isoen_US
dc.relation.ispartofCenter for Dynamics and Control of Materials Publications
dc.rights.restrictionOpen
dc.subjectGraphene
dc.titleLattice Collective Modes from a Continuum Model of Magic-Angle Twisted Bilayer Graphene
dc.typeArticle

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