Self-organized electronic order in thin exfoliated layered transition metal dichalcogenides

了解以薄膜形式存在的固体的物理性质，特别是电子性质是现代凝聚态物理学中最有趣的课题之一。申请人建议研究选定的层状过渡金属二硫族化物（TMDs）的薄剥离薄片中的电子顺序作为厚度的函数。由于层之间的弱键合，传统上认为tmd即使以其体形式也可以实现二维系统。然而，我们之前的工作表明，这幅图需要重新考虑，因为密度泛函理论有强有力的证据表明，与层平行的电子结构明显依赖于电子有序层在垂直方向上的堆叠。这些结果最近得到了宏观性质测量的支持，这些测量报告了大量材料的显著变化，作为厚度的函数，即使是中等厚度的样品，在$ $约100层的范围内。尽管如此，起作用的微观机制仍然难以捉摸。因此，申请人打算结合角度分辨光谱学、最先进的x射线散射技术和密度泛函理论，以全面了解tmd中电子结构和电子顺序向二维极限的演变。这不仅会引起基础研究的兴趣，而且还会为未来的设备应用提供极其重要的信息。此外，计划中的项目为获得新的科学技能和扩大申请人的国际经验提供了一个独特的机会。拟议的项目将在加拿大温哥华的Steward bluson量子物质研究所执行。

To understand the physical and in particular electronic properties of solids in form of thin films is one of the most intriguing topics in modern condensed matter physics. The applicant proposes to study the electronic order in thin exfoliated flakes of selected layered transition metal dichalcogenides (TMDs) as a function of thickness. Due to the weak bonding between the layers, the TMDs are traditionally believed to realize rather two-dimensional systems even in their bulk form. However, our previous work indicated that this picture needs to be reconsidered as there is strong evidence from density functional theory that the electronic structure parallel to the layers markedly depends on the stacking of the electronically ordered layers in the perpendicular direction. These results recently received support by measurements of macroscopic properties which reported significant changes as a function of thickness for a wide range of materials even for moderately thick samples in the range of $\approx$ 100 layers. Nonetheless, the microscopic mechanism at work remains widely elusive.The applicant therefore intends to combine angle-resolved photoemission spectroscopy, state-of-the-art x-ray scattering techniques and density functional theory in order to obtain a holistic understanding of the evolution of the electronic structure and the electronic order towards the two-dimensional limit in TMDs. This will not only be of interest for fundamental research but will also deliver exceedingly important information with respect to future device applications. Furthermore, the planned project provides a unique opportunity to acquire new scientific skills and to widen the international experience of the applicant. The proposed project will be executed at the Steward Blusson Quantum Matter Institute in Vancouver, Canada.