Project Details
Projekt
Structure and proximity effects in (twisted) multilayer graphene
Applicants
Professor Dr. Christian Kumpf; Dr. Felix Lüpke
Subject Area
Experimental Condensed Matter Physics
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 449119662
Epitaxial graphene serves as a promising platform for scalable two-dimensional electronics with tunable functionality through moiré and proximity effects: The intercalation of atomic species, either between the graphene and its growth substrate or between multiple graphene layers, allows to tune the electronic properties of the graphene and induces correlated electronic states, such as Mott insulators and superconductivity. The underlying mechanism are, e.g., the formation of superlattices or induced strong doping in the graphene, depending on the specific intercalant species. Furthermore, twisted graphene layers, which consist of two or more graphene sheets rotated relative to each other, have garnered significant interest for their ability to host tunable correlated electronic phases arising from moiré lattice effects. At a specific "magic" twist angle of 1.1°, twisted bilayer graphene exhibits tunable correlated insulating states and superconductivity. However, achieving such small twist angles through epitaxial methods is challenging due to lattice instabilities. In contrast, larger twist angles (20–30°) promise greater stability, while also offering intriguing electronic properties, such as alternating gapped and non-gapped regions induced by local symmetry, the formation of geometrically frustrated networks of topologically protected states, and the emergence of higher-order topological phases with fractional electron charge corner states. Despite its promising properties, large angle twisted bilayer graphene remains much less explored. As part of FOR5242, we will realize large angle twisted bilayer graphene based on epitaxial growth, in combination with intercalation and exfoliated layers. Our goal is to explore the interplay of moiré and proximity effects from the different sources and employ it to realize novel correlated electronic phases. Twisted bilayer graphene samples will be fabricated at Forschungszentrum Jülich and will be intercalated by other members of the FOR5242 consortium. Intercalated samples from the consortium will be characterized in Jülich using X-ray standing waves (XSW), angle-resolved photoemission spectroscopy (ARPES) and scanning probe microscopy (SPM), which, in combination with further characterization by the consortium member, will provide a comprehensive structural and electronic analysis of this promising material platform.
DFG Programme
Research Units
