A collaboration between researchers from Tsinghua Shenzhen International Graduate School (Tsinghua SIGS) and UC Berkeley has reported the first experimental observation of modulated optical transitions in large-angle twisted monolayer/bilayer phosphorene. Published in the international journal Nature Communications, their work highlights exciting opportunities to explore moiré physics in phosphorene and other van der Waals heterostructures with different lattice configurations.
Stacked two-dimensional (2D) materials with a finite angle generate moiré superlattices, which are characterized by a periodical variation of interlayer stacking orders. This new periodicity strongly modulates the electron’s behavior in moiré materials, giving rise to many fantastic quantum phenomena such as superconductive states, correlated insulating states, and magnetism in “magic angle” twisted bilayer graphene. So far, the moiré effect has only been reported in graphene, hexagonal boron nitride, and transition metal dichalcogenide based van der Waals heterostructures with small twist-angle. Therefore, it is highly desirable to explore moiré effects in different lattice configurations and within a large angle range.
Fig. 1. Rectangular moiré superlattice.
The team, led by Tsinghua SIGS Associate Profs. Liu Bilu, Zou Xiaolong, Prof. Cheng Hui-Ming, and UC Berkeley Prof. Wang Feng, revealed the emerging anisotropic optical transitions in large-angle twisted monolayer/bilayer phosphorene. Experiments indicated that the optical transitions were strongly modulated by the rectangular moiré superlattices. Density functional theory calculations disclosed that the profound moiré effects originated from the Γ-point direct bandgap transitions and the underlying Bloch wavefunction hybridization in both conduction band minimum (CBM) and valence band maximum (VBM) of the 20° twisted monolayer/bilayer phosphorene.
Their work enlarges the moiré materials family and renders twisted phosphorenes an attractive system to investigate moiré physics.
Fig. 2. Moire optical transitions in twisted monolayer/bilayer phosphorene.
The first authors of the article entitled “Anisotropic moiré optical transitions in twisted monolayer/bilayer phosphorene heterostructures” are Dr. Zhao Shilong and Master’s student Wang Erqing from Tsinghua SIGS. Corresponding authors are Associate Profs. Liu Bilu, Zou Xiaolong, and Prof. Wang Feng. Prof. Cheng Hui-Ming and Master’s student Tan Junyang are among the other authors of this work.
Link to full article:
Writers: Wang Erqing, Zhao Shilong
Editor: Karen Lee