Recent Advances in Moir Superlattice Systems by Angle-Resolved Photoemission Spectroscopy

The last decade has witnessed a flourish in 2D materials including graphene and transition metal dichalcogenides (TMDs) as atomic-scale Legos. Artificial moire superlattices via stacking 2D materials with a twist angle and/or a lattice mismatch have recently become a fertile playground exhibiting a plethora of emergent properties beyond their building blocks. These rich quantum phenomena stem from their nontrivial electronic structures that are effectively tuned by the moire periodicity. Modern angle-resolved photoemission spectroscopy (ARPES) can directly visualize electronic structures with decent momentum, energy, and spatial resolution, thus can provide enlightening insights into fundamental physics in moire superlattice systems and guides for designing novel devices. In this review, first, a brief introduction is given on advanced ARPES techniques and basic ideas of band structures in a moire superlattice system. Then ARPES research results of various moire superlattice systems are highlighted, including graphene on substrates with small lattice mismatches, twisted graphene/TMD moire systems, and high-order moire superlattice systems. Finally, it discusses important questions that remain open, challenges in current experimental investigations, and presents an outlook on this field of research. Artificial moire superlattices have become a fertile playground for emergent quantum phenomena. Modern angle-resolved photoemission spectroscopy (ARPES) can directly visualize electronic structures and thus can provide enlightening insights into fundamental physics in moire superlattice systems and guides for designing novel devices. Major advances in the ARPES studies of moire superlattices are reviewed and new experimental directions are discussed.image