Interplay between frustrated, correlated and topological quantum electronic states in magnetic kagome metals

• Applicant: Dr. Ece Uykur
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449920715

The magnetic kagome metals are newly emerged family of the topologically nontrivial materials. They are attracted a lot of attention, because the underlying kagome structure of the compounds give rise to numerous interesting properties. It is theoretically known that an ideal kagome network has certain implications on the band structure. It is expected to create a flat band accompanied by two linearly dispersing bands, i.e. an unusual setting brings together two dissimilar features in the electronic structure of the magnetic kagome metals: the dispersionless flat bands host localized massive electrons and linearly dispersing bands possess massless Dirac fermions. The strong electronic correlations and magnetism led in the former and the topological nature of the latter opens a new avenue to create multitude of exotic phenomena. FeSn-binary compounds are proposed as one of the promising candidates of the magnetic kagome metals. This project aims to initiate a systematic optical study on FeSn-binary compounds to investigate the interplay between magnetism, electronic correlations, and topological orders and their relation to the geometrical frustration. The optical conductivities of three polymorphs, namely FeSn (2D), Fe3Sn2 (quasi-2D), and Fe3Sn (3D) will be investigated in broad energy, temperature, and pressure range: (i) The optical fingerprints of the flat bands and the Dirac fermions in the magnetic kagome metals will be identified. (ii) By studying the different polymorphs, we will tune the interlayer coupling between the kagome networks and correspondingly the electronic and magnetic structure. (iii) The effect of the dimension and the crystal structure on optical properties will be clarified. (iv) External pressure, on the other hand, will change the intra-kagome as well as the inter-kagome coupling. These two effects will be separated with comparison to the compound tuning. (v) External pressure will also be used to tune the flat bands and the Dirac fermions. The interactions between these two states and the optical signatures will be investigated.

• DFG Programme: Research Grants