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MoS2, as a typical material of two-dimensional semiconductor transition metal chalcogenides, has excellent physical properties such as tunable band gap. Therefore, MoS2 moiré superlattice is an ideal system for investigating the electron transport in condensed matter and the design of optoelectronic devices. On the other hand, interlayer conductance serves as a significant indicator for analyzing coupling effects in moiré superlattice. Here, in order to clarify the influence of tunable band gap on the interlayer conductance, we develop a tunneling theory for calculating the interlayer conductance of MoS2 moiré superlattices by using optical methods in diffraction physics. In this theory, the electron tunneling can be considered as the diffraction of electron waves by the periodic gratings. Accordingly, the influences of the periodicity of MoS2 moiré superlattices and the coherence of the tunneling electrons can be well included in the theory. In addition, the effect of the tunable band gap of MoS2 is taken into account. According to the theory, we investigate the properties of the interlayer conductance of MoS2 moiré superlattice. The theoretical results show that due to the diffraction effect, there exist two partial waves of the tunneling electron at the interface, which can resonate with the interface potential. Accordingly, the interlayer conductance curves exhibit a double-peak structure. Furthermore, we analyze the influences of the tunneling layer and the metal electrodes on the interlayer conductance: the thickness of the upper MoS2 lattice affects the peak and the lower one primarily influences the background. The coherence of tunneling electrons will be enhanced when the parameter of interface potential strength increases. The chemical potential of the metal electrode mainly affects the properties of the peak, and the influence is more significant than that in graphite moiré superlattice.
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Keywords:
- MoS2 moiré superlattice /
- tunneling conductance /
- diffraction physics /
- twistronics
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图 1 (a) MoS2莫尔超晶格体系示意图; (b) MoS2莫尔超晶格的俯视图
Figure 1. (a) Schematic illustration of MoS2 moiré superlattices; (b) Top view of MoS2 moiré superlattices.
图 2 不同上层厚度下关于扭转角的层间电导曲线, 内插图为d1 = 2.60 nm时电导峰的放大图
Figure 2. Interlayer conductance curves versus twist angle under different d1, and the inset is the enlarged figure of the peak of d1 = 2.60 nm.
图 3 (a)不同下层厚度下关于扭转角的层间电导曲线; (b)当扭转角α分别为0°和10°时层间电导背景随下层厚度的变化曲线, 其中对应于整数层厚度的数据点为空心符号所标注
Figure 3. (a) Interlayer conductance curves versus twist angle under different d2; (b) the background as a function of d2 under different twist angles, and the data corresponding to the discrete layers are marked with open symbols.
图 4 不同界面势强度参数下关于扭转角的层间电导曲线, 内插图为γ0 = 4×10–29 J·m和γ0 = 5×10–29 J·m时电导峰的放大图
Figure 4. Interlayer conductance curves versus twist angle under different γ0, and the inset is the enlarged figure of the peaks of γ0 = 4×10–29 J·m and γ0 = 5×10–29 J·m.
图 5 不同化学势μ下关于扭转角的层间电导曲线
Figure 5. Interlayer conductance curves versus twist angle under different μ.
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