Figure 2| Interlayer exciton transport under moiré potential. (IMAGE)
Caption
a Optical image of two CVD-grown WS2/WSe2 heterobilayers with twist angles of 0 and 60° on the same WS2 underlayer. b High-resolution annular dark-field scanning transmission electron microscopy image of the 60° heterobilayer. The white diamond outline shows the moiré superlattice with a periodicity of ~7.6?nm. c Schematic illustration of the WS2/WSe2 heterobilayer with a type-II band alignment to facilitate the interlayer exciton formation. d Schematic representation of a typical electronic band structure of a WS2/WSe2 heterobilayer in a (strained) primitive unit cell. The four lowest-energy transitions are indicated by arrows (K-K valley transitions are denoted by vertical arrows 1 and 2, and K-Q valley transitions are denoted by vertical arrows 3 and 4). The K-K transitions in individual WS2 and WSe2 monolayers are marked by vertical arrows WS2 and WSe2, respectively. e Approximate moiré potentials for the twist angles of 0° (left) and 60° (right) plotted along the main diagonal of the moiré supercells (black lines in f). f, g Illustrations of the 2D K-K moiré potentials in both 3D graphs and 2D projections to trap interlayer excitons (red and black spheres) in the local minima for 0° (f) and 60° (g) heterobilayers. h Time-dependent mean squared distances (σt2-σ02) travelled by interlayer excitons in 0° and 60° heterobilayers as well as by intralayer excitons in WS2 and WSe2 monolayers (1L-WS2, 1L-WSe2). i Exciton density-dependent interlayer exciton transport at room temperature for the 60° heterobilayer. j Temperature-dependent interlayer exciton transport for the 60° heterobilayer.
Credit
by Ying Jiang, Shula Chen, Weihao Zheng, Biyuan Zheng and Anlian Pan
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