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作为二维半导体过渡金属硫族化物中的典型代表性材料， MoS2具有带隙可调谐特性等优异物理特性。因此， MoS2莫尔超晶格是研究凝聚态电子输运问题和设计光电器件的理想体系。另一方面，层间电导的测量是研究莫尔超晶格层间耦合作用的重要手段。为了阐明带隙可调谐等特性对莫尔超晶格层间电导的影响，有必要对MoS2莫尔超晶格的层间电导特性加以研究。本文利用衍射物理中的光学方法，构建了MoS2莫尔超晶格体系的隧穿理论。在该理论中，将MoS2莫尔超晶格中电子的隧穿视作电子波为周期性光栅所散射。利用该理论，本文研究了MoS2莫尔超晶格的层间电导特性。研究结果表明：由于衍射效应，界面处隧穿电子波存在两个分波均与界面势产生共振，所以层间电导随扭转角的变化曲线呈现双峰结构。进一步地，本文还研究了隧穿层和金属电极对层间电导的影响：上层和下层MoS2晶格厚度分别影响层间电导的峰和背景；界面势强度的增大可以增强隧穿电子的相干性；金属电极化学势主要影响MoS2莫尔超晶格层间电导峰的特性，且相比于石墨莫尔超晶格，影响更为显著。As a typical material of two-dimensional semiconductor transition metal chalcogenides, MoS2 has excellent physical properties such as tunable band gap. Therefore, MoS2 moirésuperlattice 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 have developed 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. Based on the theory, we have investigated the properties of the interlayer conductance of MoS2 moirésuperlattice. 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 have analyzed the influences of the tunneling layer and the metal electrodes to the interlayer conductance: the thicknesses of the upper MoS2 lattice affects the peak and the lower one primarily influence 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 influences the properties of the peak, and the influence is more significant than that in graphite moirésuperlattice.
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Keywords:
- MoS2 moiré superlattice /
- tunneling conductance /
- diffraction physics /
- twistronics
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