Moire physics in twisted van der Waals heterostructures of 2D materials

摘要

Artificial moire superlattices are formed by vertically stacking two monolayers of two-dimensional (2D) materials and rotating one of the layers with a finite twist angle. The resultant moire pattern in the twisted heterostructures exhibits periodic length scale larger than that of lattice atoms of the individual layers. Furthermore, the moire pattern is found to control the interlayer hybridization in a twisted bilayer heterostructure creating strongly correlated quantum states. Owing to the moire pattern-introduced interlayer hybridization, several exotic quantum phenomena such as flat bands, moire excitons, surface plasmon polaritons, surface phonon polaritons, surface exciton polaritons, interlayer magnetism, and 2D ferroelectricity are recently found in the engineered materials with additional twist degree of freedom. Here we review some notable advances in moire physics associated with twisted bilayer heterostructures of 2D crystals including (A) flat bands in the twisted bilayer graphene, (B) exciton superlattices in the twisted transition metal dichalcogenides, (C) topological polaritons and photonic superlattices in the twisted 2D metal oxides, (D) interlayer magnetism in the stacked 2D magnetic semiconductors, and (E) ferroelectricity in moire quantum materials. This story-of-twist begins with (1) an introduction to twisted heterostructures, (2) a correlation between van der Waals heterostructures and moire superlattices, (3) how to design and fabricate moire quantum materials, (4) discussion on five emergent quantum phenomena associated with twisted bilayer heterostructures as listed above, and finally (5) what are the challenges in fabrication, characterization, and applications of twisted heterostructures. This review concludes with an outlook pointing toward innovation in large-area design of twisted heterostructures for their potential applications in quantum nanoelectronics, quantum photonics, optoelectronics, quantum computing, nonvolatile memory, quantum emission, and quantum communication. Moire physics of moire quantum materials is a relatively new and extremely exciting area of research. This article provides a general overview of recent advances of moire physics in twisted van der Waals heterostructures of 2D materials.