FWF - AbInitio - Ab Initio Theory of Superconducting Two-Dimensional Crystals

The aim of this research project is to improve the physical understanding of superconductivity in two-dimensional transition metal dichalcogenides and to investigate properties of the superconducting phase from first-principles. Recent studies have shown that the dimensionality of materials is one of the most important factors determining their physical behaviour. This dependence of the physical properties on the dimension is markedly demonstrated in the family of transition metal dichalcogenides. These materials are chemically extremely diverse, resulting in a variety of different compounds ranging from insulators to semiconductors, semimetals and metals. Because of this diversity, they are especially interesting for technological applications in nanoelectronics and optoelectronics, such as monolayer field-effect transistors, flexible electronic devices and energy storage. Additionally, fascinating collective phases like charge density waves, superconductivity and Mott transitions have been observed, making these materials ideal candidates to investigate the effects of reduced dimensionality. With this project, we want to elucidate the atomic-scale mechanisms underpinning superconductivity in two-dimensional transition metal dichalcogenides on a fundamental level. We will investigate the interplay of phonon, charge and spin interactions, and quantitatively determine key properties of the superconducting regime fully from first-principles. To this end, we will employ many-body Green's function techniques and develop a completely ab initio method to describe the occurring pairing channels leading to superconductivity. This will enable us to study the dependence of the critical superconducting temperature and of the energy gap function on pressure, doping and layer thickness in these materials. Moreover, the availability of a method to describe superconductivity without the need for empirical parameters will permit the ab initio prediction of new superconducting compounds with specifically designed properties. We are confident that the results of this project will be of great interest to the scientific community and that they will help to advance the knowledge on two-dimensional systems and superconductivity in general. Additionally, as the transition metal dichalcogenides are promising for a wide range of future applications, our findings might prove to be of substantial benefit for technological research as well.