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Recently, the kagome superconductor family AV₃Sb₅ (A = K, Rb, Cs) has been heavily investigated due to its interesting lattice and the occurrence of a charge density wave (CDW). Especially, the origin of the instability and its connection to superconductivity is intensely discussed. Among the most common proposed explanations for the CDW is Fermi surface nesting, influence of van-Hove-singularities and matrix element effects [1,2,3]. However, a clear cut identification is still outstanding.

By utilizing phonon fluctuation diagnostics [4] we try to pinpoint the electronic processes behind phonon softening​. This allows us to disentangle fermiology and matrix-element effects and thereby enhance the understanding of the CDW origin. 

[1] M. Kang, et al., Nat. Phys. 18, 301–308 (2022)

[2] X. Wu, et al., Phys. Rev. Lett. 127, 177001

[3] H. Luo, et al., Nat Commun 13, 273 (2022)

[4] J. Berges et al., Phys. Rev. B 101, 155107 (2020)​