Gap Opening in Twisted Double Bilayer Graphene by Crystal Fields

dc.contributorAalto Universityen
dc.contributor.authorRickhaus, Peteren_US
dc.contributor.authorZheng, Giuliaen_US
dc.contributor.authorLado, Jose L.en_US
dc.contributor.authorLee, Yongjinen_US
dc.contributor.authorKurzmann, Annikaen_US
dc.contributor.authorEich, Mariusen_US
dc.contributor.authorPisoni, Riccardoen_US
dc.contributor.authorTong, Chuyaoen_US
dc.contributor.authorGarreis, Rebekkaen_US
dc.contributor.authorGold, Carolinen_US
dc.contributor.authorMasseroni, Micheleen_US
dc.contributor.authorTaniguchi, Takashien_US
dc.contributor.authorWantanabe, Kenjien_US
dc.contributor.authorIhn, Thomasen_US
dc.contributor.authorEnsslin, Klausen_US
dc.contributor.departmentDepartment of Applied Physicsen
dc.contributor.groupauthorCorrelated Quantum Materials (CQM)en
dc.contributor.organizationSwiss Federal Institute of Technology Zurichen_US
dc.contributor.organizationNational Institute for Materials Scienceen_US
dc.description| openaire: EC/H2020/766025/EU//QuESTech
dc.description.abstractCrystal fields occur due to a potential difference between chemically different atomic species. In van der Waals heterostructures such fields are naturally present perpendicular to the planes. It has been realized recently that twisted graphene multilayers provide powerful playgrounds to engineer electronic properties by the number of layers, the twist angle, applied electric biases, electronic interactions, and elastic relaxations, but crystal fields have not received the attention they deserve. Here, we show that the band structure of large-angle twisted double bilayer graphene is strongly modified by crystal fields. In particular, we experimentally demonstrate that twisted double bilayer graphene, encapsulated between hBN layers, exhibits an intrinsic band gap. By the application of an external field, the gaps in the individual bilayers can be closed, allowing to determine the crystal fields. We find that crystal fields point from the outer to the inner layers with strengths in the bottom/top bilayer Eb = 0.13 V/nm ≈ -Et = 0.12 V/nm. We show both by means of first-principles calculations and low energy models that crystal fields open a band gap in the ground state. Our results put forward a physical scenario in which a crystal field effect in carbon substantially impacts the low energy properties of twisted double bilayer graphene, suggesting that such contributions must be taken into account in other regimes to faithfully predict the electronic properties of twisted graphene multilayers.en
dc.description.versionPeer revieweden
dc.identifier.citationRickhaus, P, Zheng, G, Lado, J L, Lee, Y, Kurzmann, A, Eich, M, Pisoni, R, Tong, C, Garreis, R, Gold, C, Masseroni, M, Taniguchi, T, Wantanabe, K, Ihn, T & Ensslin, K 2019, ' Gap Opening in Twisted Double Bilayer Graphene by Crystal Fields ', Nano Letters, vol. 19, no. 12, pp. 8821-8828 .
dc.identifier.otherPURE UUID: c49765bc-e23d-4500-a4ce-6c6240fa0c08en_US
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dc.relation.ispartofseriesNano Lettersen
dc.relation.ispartofseriesVolume 19, issue 12en
dc.subject.keywordbilayer grapheneen_US
dc.subject.keywordcrystal fielden_US
dc.subject.keywordfield induceden_US
dc.subject.keywordp-n junctionen_US
dc.titleGap Opening in Twisted Double Bilayer Graphene by Crystal Fieldsen
dc.typeA1 Alkuperäisartikkeli tieteellisessä aikakauslehdessäfi