Low temperature lattice distortion in the kagome FeGe

A new family of kagome metals has emerged as a fertile playground to investigate correlation-driven topological phases. Among them, FeGe has been observed to host charge density waves and magnetism at 100 K and 400 K, respectively. Our diffuse scattering data indicates that the CDW results from a simultaneous condensation of phonons at L (½ 0 ½) and M points (½ 0 0) of the BZ. Besides, a third CDW propagation vector with QCDW=0 0 ½ is observed below 100 K and interpreted as dimerization driven CDW. In this proposal, we want to solve the low temperature CDW phase of FeGe and discern whether dimerization, nesting or a disorder scenario are responsible for the charge modulations reported. For this, hard x-ray diffraction will provide the complete set of data and will allow us to understand the origin of the CDW in FeGe and learn how magnetism intertwins with the charge order. The results will be of extreme importance for the rapidly grown field of correlated topology and flat bands.