Valentin Crepel (Flatiron Institute): Condensed & Living Matter Seminar

Title: “Robust prediction of moiré material topology”

Valentin Crepel

Flatiron Institute

Research Synopsis:

Moiré materials have recently been envisioned as condensed-matter quantum simulators [1] due to their highly tunable low-energy properties controlled by chemical composition, stacking configurations, twist angles, and gating. Realizing their full potential as practical quantum simulators requires a systematic approach to identify which heterostructures are best suited for stabilizing specific target phases of matter; something that still crucially lacks. This gap is evident in the theoretically unexpected discovery of topological phases in penta-layer graphene, as well as the strikingly different phase diagrams of twisted WSe2 and MoTe2 bilayers, despite their elementary constituent being governed by similar underlying physics.

In this talk, I will present some recent efforts aimed at filling this gap and predicting the emergence of topological phases in moiré materials [2,3]. I will begin by providing a microscopic understanding of the interlayer couplings that promote topology in a particular class of materials. Next, I will introduce a systematic and computationally efficient method to extend this microscopic understanding to a wide range of heterostructures. Finally, I will address the effects of interactions and demonstrate how this approach can be adapted to capture the physics of penta-layer graphene.

[1] Kennes, D. M., Claassen, M., Xian, L., Georges, A., Millis, A. J., Hone, J., … & Rubio, A. (2021). Moiré heterostructures as a condensed-matter quantum simulator. Nature Physics, 17(2), 155-163.

[2] Crépel, V., & Millis, A. (2024). Bridging the small and large in twisted transition metal dichalcogenide homobilayers: A tight binding model capturing orbital interference and topology across a wide range of twist angles. Physical Review Research, 6(3), 033127.

[3] Crépel, V., & Cano, J. (2025). Efficient prediction of superlattice and anomalous miniband topology from quantum geometry. Physical Review X (15) 011004.