Programme

I.5 -- Invited, VCTP-47

Date: Monday, 1 August 2022

Time: 16:00 - 16:30

Online presentation

Electronic properties and related features in twisted graphene systems

Viet-Hung Nguyen and Jean-Christophe Charlier

Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium

In recent years, stacking two-dimensional crystals to form new materials has proved relatively easy, as the van der Waals forces between successive layers are weak, to explore a broad range of novel physical and chemical properties [1]. Furthermore, this versatile method adds some degrees of freedom which can be exploited to devise heterostructures with new properties, different from the simple combination of properties of the individual materials forming the stack. Remarkably, the misorientation (characterized by the twist angle) and/or lattice mismatch between successive 2D crystals creates long-range super-periodicity known as moiré [2,3]. The effect of the twist angle and its associated moiré is particularly spectacular when considering electrical, magnetic and optical properties. In particular, twisted bilayer graphene can switch from insulating to superconducting, or to more exotic quantum or topological phases due to strong electronic correlations at low twist angle. Such observations have been considered as real scientific breakthroughs, creating a nascent field of “twistronics” [4], i.e. aiming to explore novel physical properties in vertically stacked 2D structures when tuning the twist angle between the related layers. In this talk, we will present an overview of our recent researches [5-8] related to the electronic properties of twisted graphene systems. These researches centred on the understanding of the interplay between atomic-scale structure (i.e., created moiré superlattices) and electronic properties in the mentioned twisted systems. References: [1] A. Geim and I. Grigorieva, Van der Waals heterostructures, Nature 499, 419-425 (2013). [2] E. Y. Andrei and A. H. MacDonald, Graphene bilayers with a twist, Nat. Mater. 19, 1265-1275 (2020). [3] F. He, Y. Zhou, Z. Ye, S.-H. Cho, J. Jeong, X. Meng, and Y. Wang, Moiré Patterns in 2D Materials: A Review, ACS Nano 15, 5944-5958 (2021). [4] Z. Hennighausen and S. Kar, Twistronics: a turning point in 2D quantum materials, Electron. Struct. 3, 014004 (2021). [5] A.C. Gadelha, D. A. A. Ohlberg, C. Rabelo, et al., Localization of lattice dynamics in low-angle twisted bilayer graphene, Nature 590, 405-409 (2021). [6] V. Hung Nguyen, et al., Electronic localization in small-angle twisted bilayer graphene, 2D Mater. 8, 035046 (2021). [7] A. C. Gadelha, V. Hung Nguyen, et al., Electron-phonon coupling in a magic-angle twisted-bilayer graphene device, arXiv:2110.14916 (2021). [8] V Hung Nguyen, et al., Electronic properties of twisted multilayer graphene, J. Phys. Mater. 5, 034003 (2022).

Presenter: Nguyen Viet Hung