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

• Applicant: Dr. Tobias Ritschel, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2017 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 387615343

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.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Hosts: Professor Dr. Andrea Damascelli; Professor Dr. George Albert Sawatzky