The long range electronic modulations recently discovered in the geometrically frustrated kagome lattice have opened new avenues to explore the effect of correlations in materials with topological electron flat bands [1]. In this talk, I will present ARPES, diffuse scattering and inelastic x-ray scattering (IXS) data in several kagome metals that allow a comprehensive study their phase transitions. I will focus on the recently discovered multiple-q charge modulations in (Cs,Rb)V3Sb5 [2], FeGe [3]and ScV6Sn6 [4] and explain how their dynamics follow either an order-disorder scenario common in first order phase transformations or a phonon softening characteristic of a second order phase transition. Furthermore, I will show the potential of diffuse scattering to identify primary order parameters and its coupling/competition to secondary orders in the study of multiple-q charge density waves in materials hosting correlated flat phonon-topological flat electron physics.
Figure 1: Momentum dependence of the 1/3 1/3 13/2 phonon frequency at selected temperatures, highlighting the large momentum softening in ScV6Sn6.
References
[1] B. R. Ortiz et al., Phys. Rev. Materials 3, 094407 (2018). [2] D. Subires et al., Nat. Comm. 14, 1015 (2023) [3] D. Subires et al., in preparation [4] A. Korshunov et al., Nature Comm. 14, 6646 (2023).
