Fig. 3: Phonon band structures and mode mixing in the process of CDW distortion.
From: Observation of anomalous amplitude modes in the kagome metal CsV3Sb5
a Phonon band structures directly calculated by DFT. Here, 100% (0%) refers to the fully stable ISD (2 × 2 pristine) structure. 10% refers to the intermediate structure with 10% distortion from the pristine to ISD phases. After 2 × 2 × 1 band folding with no distortion, three imaginary modes (\({M}_{1}^{+}\)) are folded to Γ. A weak ISD-type distortion lifts the degeneracy and leads to A1g and E2g modes. The ISD distortion gradually transforms imaginary modes to real. b Projections of the imaginary A1g (E2g) mode with 10% distortion to all the other phonon modes at Γ, as evolving into the stable ISD phase (100%). We highlight all A1g and E2g modes by orange and blue dots, respectively, at the Γ point. The dashed orange (blue) curve in (b) guides eyes to show the evolution of the imaginary A2 (E1) modes in the CDW distortion.
