Ding PEI : nano-ARPES study on moiré superlattices

Moiré superlattices are formed when two layers of van der Waals (vdW) materials with a slight twist angle or lattice mismatch are stacked together. In such a superlattice, original electronic bands of the constituent layer are folded into a reduced Brillouin zone (BZ), or mini-BZ, due to the enlarged moiré lattice constant, which can give rise to isolated flat moiré bands under suitable conditions (e.g., specific twist angle or lattice relaxation, etc.). At proper filling level, these moiré bands can lead to rich interesting quantum phases, such as correlated insulator, superconductor, or quantized anomalous Hall insulator.

Angle-resolved photoemission spectroscopy with sub-micron spatial resolution (nano-ARPES) is a powerful tool for probing the momentum-resolved electronic structure of moiré superlattices. In this talk, I will first introduce the principles of nano-ARPES and the practical aspects of performing such measurements. I will then present and discuss recent nano-ARPES results on various moiré systems, including twisted bilayer graphene, twisted transition metal dichalcogenides, and other vdW heterostructures [1-2]. Finally, I will introduce the latest developments at the nano-ARPES beamline at Synchrotron SOLEIL, with a particular focus on the new capability to perform ARPES measurements under controllable magnetic fields [3].

[1] D. Pei, et al., Physical Review X 12 (2), 021065 (2022)

[2] D. Pei, et al., Nano Letters 23 (15), 7008-7013 (2023)

[3] J. Huang, et al., Review of Scientific Instruments 94, 9 (2023)