B07 N

Spin and orbital textures in kagome superconductors

Summary

For the third funding period of the SFB 1170, we are applying for a new project that responds directly to recent research developments aiming to investigate topological Kagome superconductors using advanced angle-resolved photoelectron spectroscopy (ARPES) techniques. In particular, the focus will be on the compounds AV3Sb5 (A = Cs, K, Rb), in which the two-dimensional V-layers form ideal Kagome lattices. Access to high-quality single crystals has been already provided by external col- laborators. By featuring a plethora of physical phenomena, such as superconductivity, chiral charge order, topological Dirac physics, and unconventional time-reversal symmetry breaking in absence of any net magnetization, these materials represent perfect internal hybrid systems and provide a playground for theoretical and experimental investigations of the interplay between topology, charge ordering, and superconductivity. As such, this project is well suited to the research scope of the SFB 1170 and particularly contribute to the research objectives of Area B. The main focus of our project will be to experimentally probe the momentum space texture of the electronic wave functions. More precisely, the idea is to use ARPES combined with linear and circular dichroism in order to access the pairing mechanism and topological properties of the Kagome systems. Within recent research projects, we have shown that dichroic ARPES is a very powerful tool for those purposes. For exam- ple, in Weyl semimetals hosting chiral Weyl fermions in their bulk band structure, this method provides a momentum-resolved probe of the characteristic topological Berry phase winding around the chiral quasiparticle excitations. We are now aiming to transfer this approach to address the proposed chiral charge order and topological (Dirac) physics in AV3 Sb5 both of which should likely affect the mo- mentum space spin- and orbital textures as well as the Berry curvature. The experiments have to be systematically taken as a function of photon energy and sample temperature, particularly across the charge ordering transition temperature. Moreover, the experimental data shall be supported from state-of-the-art photoemission and density functional theory calculations. For both, we receive direct support from collaborators within the SFB 1170. Overall, our activities will be strongly connected to other experimental and theory-based projects. In particular, we will use the synergy that the PIs have built up with the theory projects B06 and C05 during the second funding period.