Moiré plane wave expansion model for simulating STM images of incommensurate 2D materials

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Moiré plane wave expansion for simulating STM
2024. 05. 10. 10:15
BME building F, seminar room of the Dept. of Theoretical Physics
Maxime Le Ster (Lodz)
Moiré systems have recently attracted a lot of attention in condensed-matter physics following the experimental discovery of superconductivity in twisted bilayer graphene [1]. A whole plethora of other unique quantum phases of matter have been since explored, with most theoretical investigations focusing on the emergence of flat bands and correlated electronics [2]. Scanning tunneling microscopy (STM) simulations of moiré systems have however been overlooked, despite moiré patterns almost always arising from the pairing of two-dimensional (2D) materials and the potential assistance that simulations could provide for scientists investigating van der Waals heterostructures. Indeed, moiré patterns can sometimes lead to complex STM images, especially true in the case of mixed symmetry coupling, i.e., hexagonal-rectangular symmetry pairing [3, 4]. In these systems, the moiré unit cell can be very large and even infinite for the incommensurate case, excluding the application of methods based on periodic cells, e.g., density functional theory. Other approaches are thus required; in this talk, I will introduce a new method, the moiré plane wave expansion model (MPWEM), to simulate STM images, which simply requires a priori knowledge of the non-interacting STM images and a small set of intuitive parameters [5].
[1] Y. Cao et al., Nature 556, 43-50 (2018)
[2] D. M. Kennes et al., Nat. Phys. 17, 155-163 (2021)
[3] M. Le Ster et al., Phys. Rev. B 99, 075422 (2019)
[4] M. Le Ster et al., 2D Mater. 7, 011005 (2019)
[5] M. Le Ster et al., submitted.