2025/10/23 by Wang, Yifan, Xu, Chenchao, Wu, Zhimian +11
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el) #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.2510.20230
A range of of unusual emergent behaviors have been reported in the charge-density wave (CDW) state of the AV3Sb5 (A=~K, Rb, Cs) kagome metals, including a CDW formation process without soft phonons, which points to an unconventional CDW mechanism. Here, we use inelastic x-ray scattering to show that the CDW in KV3Sb5 forms via phonons that soften to zero energy at the CDW ordering vector (L-point) around T\rm CDW=78~K. These soft phonons exhibit a remarkable in-plane anisotropy, extending over a much larger momentum range along L-A relative to L-H, which leads to diffuse scattering common among AV3Sb5. Using first-principles calculations, we find that the momentum-dependent electron-phonon coupling (EPC) is peaked at L and exhibits the same in-plane anisotropy as the phonon softening. Conversely, the electronic susceptibility is not peaked at L and shows the opposite in-plane anisotropy. Our findings favor momentum-dependent EPC as the driving mechanism of the CDW in KV3Sb5, with a CDW formation process similar to that of transition metal dichalcogenides.