The phase diagram serves as a blueprint for designing the structure of a material, offering a comprehensive representation of its different phases under specific conditions, such as temperature and pressure. In the realm of two-dimensional (2D) materials, stacking order can play a crucial role in controlling and inducing phase transitions. However, in studying phase diagrams for 2D materials, the exploration of stacking degree of freedom has largely been overlooked, limiting our understanding and hindering future applications. Here, we experimentally explore the interplay of stacking and pressure degrees of freedom in revealing unique phase transitions in bilayer MoS2 with two different stacking configurations. In AA stacking, interlayer sliding and asymmetric intralayer compressing precede intralayer rotation, while in AB stacking, asymmetric intralayer compressing and intralayer distortion occur simultaneously. Under further elevated pressure, the bilayer system transitions into 1T′ phase before amorphization. Our findings offer valuable insights for creating comprehensive phase diagrams and exploring exotic phases as well as phase transitions of 2D materials in a broader parameter space.

中文翻译：

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双层 AA- 和 AB-MoS2 中新的堆积压力相图的探索


相图作为设​​计材料结构的蓝图，提供了特定条件（例如温度和压力）下不同相的全面表示。在二维（2D）材料领域，堆叠顺序在控制和诱导相变方面发挥着至关重要的作用。然而，在研究二维材料的相图时，对堆叠自由度的探索在很大程度上被忽视了，限制了我们的理解并阻碍了未来的应用。在这里，我们通过实验探索了堆叠和压力自由度的相互作用，揭示了具有两种不同堆叠配置的双层 MoS2 中独特的相变。在AA堆叠中，层间滑动和非对称层内压缩先于层内旋转，而在AB堆叠中，非对称层内压缩和层内扭曲同时发生。在进一步升高的压力下，双层系统在非晶化之前转变为 1T' 相。我们的研究结果为创建全面的相图和探索更广泛的参数空间中二维材料的奇异相和相变提供了宝贵的见解。