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

了解固体薄膜的物理性质，特别是电子性质，是现代凝聚态物理中最有趣的课题之一。 申请人提出研究所选层状过渡金属二硫属化物（TMD）的薄剥离薄片中的电子有序性作为厚度的函数。由于层之间的弱键合，传统上认为即使在其块状形式下，TMD也实现相当二维的系统。然而，我们以前的工作表明，这张照片需要重新考虑，因为有强有力的证据，从密度泛函理论的电子结构平行的层显着依赖于堆叠的电子有序层在垂直方向。这些结果最近得到支持的宏观性能的测量报告的显着变化作为一个功能的厚度为广泛的材料，甚至为中等厚度的样品在范围内的$\约$100层。因此，申请人打算将联合收割机角分辨光电子能谱、最先进的X射线散射技术和密度泛函理论相结合，以便获得对TMD中电子结构和电子有序向二维极限的演变的整体理解。 这不仅对基础研究有意义，而且还将为未来的设备应用提供极其重要的信息。 此外，计划中的项目提供了一个独特的机会，以获得新的科学技能和扩大申请人的国际经验。 拟议的项目将在加拿大温哥华的Steward Blusson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.