Topological properties of graphene moiré superlattice systems and recent optical studies
Lü Xin-Yu,Li Zhi-Qiang +1 more
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In this article, the authors review theoretical and experimental investigations of the topological properties of graphene moire superlattices, including topological domain wall states in bilayer graphene and topological effects in twisted bilayer-bilayer graphene.Abstract:
When 2D materials with different lattice constants or lattice rotation angles are stacked together, a periodic moire pattern will appear. Such moire superlattice introduces a new two dimensional periodic potential, which can greatly change the physical properties of the original systems. Recent experimental studies of moire superlattices formed by graphene on graphene and graphene on hexagonal boron nitride have revealed very rich strong correlation effects and topological effects due to novel states in superlattice minibands. It has been shown that flat bands in graphene-based moire superlattice systems can host both topological states and strongly correlated states, which can be controlled by an external electric field. In bilayer graphene, ABC stacked trilayer graphene and twisted bilayer-bilayer graphene, the number of valence and conduction bands near the Dirac point and even the band topology and bandwidth can be changed by varying the stacking angle between graphene layers or the applied bias voltage. Moreover, the competition between kinetic energy and coulomb interaction depends on the bandwidth and the external electric field, and at the so-called magic angle mott insulator states and superconductivity were observed. Twisted bilayer-bilayer graphene has also been predicted to show similar intriguing properties, including electrically tunable strongly correlated insulators, superconductivity and many rich topological states. In graphene-based moire systems, the combination of topological states and strong correlations is expected to lead to a broad range of novel phenomena that are not achievable in other material systems. Therefore, graphene moire systems is likely to bring substantial progress to the study of topological materials. In this paper, we review theoretical and experimental investigations of the topological properties of graphene moire superlattices, including topological domain wall states in bilayer graphene and topological effects in twisted bilayer graphene, ABC trilayer graphene and twisted double bilayer graphene. The origins of topological properties of these systems are discussed as well as topological phenomena observed in various experiments. Finally, recent near-field optical studies of the band structure and novel topological properties of graphene moire superlattices are discussed.read more
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Optical conductivity of twisted bilayer graphene near the magic angle
Lu Wen,Zhiqiang Li,Yan He +2 more
TL;DR: In this paper, the authors theoretically study the band structure and optical conductivity of twisted bilayer graphene (TBG) near the magic angle considering the effects of lattice relaxation, and they show that the optical conductivities spectrum is characterized by a series of peaks associated with the van Hove singularities, and the peak energies evolve systematically with the twist angle.
Journal ArticleDOI
Optical Conductivity of Twisted Bilayer Graphene Near the Magic Angle
Lu Wen,Zhiqiang Li,Yan He +2 more
TL;DR: In this paper, the authors theoretically study the band structure and optical conductivity of twisted bilayer graphene (TBG) near the magic angle considering the effects of lattice relaxation, and they show that the optical conductivities spectrum is characterized by a series of peaks associated with the van Hove singularities, and the peak energies evolve systematically with the twist angle.
Journal ArticleDOI
Study on unidirectional propagation control of helical edge states in topological spin photonic crystals
TL;DR: In this paper , the effects of geometric parameters on the bandgap structure, topological properties and unidirectional propagation of helical edge states in topological spin photonics crystals are studied in detail.
Journal ArticleDOI
Electron transport properties of order-disorder separated two-dimensional bilayer systems
TL;DR: In this article , the effects of stacking interface structure, strength of interlayer coupling and degree of disorder on the electron transport properties of order-disorder separated two-dimensional bilayer systems were systematically studied.
Journal ArticleDOI
Exciton moiré potential in twisted WSe2 homobilayers modulated by electric field
TL;DR: In this paper , the amplitude and shape of the interlayer exciton moiré potential in two stacked transition metal dichalcogenide monolayers with different rotation angles were investigated.
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