Fig. 4. Ultrafast dynamics along the c-axis of CuTe and schematics of a CDW in various dimensions.
a Normalized ΔR/R spectra of a CuTe single crystal at different incident angles, θ (ϕ1 and ϕ2 = 0°) at T = 100 K. Inset: the oscillation components of normalized ΔR/R spectra in (a) after subtracting the decay background (dashed line fitted using Eq. (1)). b Fourier transform spectra of the oscillation components in the inset of (a). c Schematics of a CDW in various dimensions for which two layers along the c-axis are anti-phase. d Modulated structure of the CDW in (c) with charge density difference between CDWc and non-CDW (normal) states obtained by first-principles calculations. An absolute isosurface value of 0.007 e/bohr3 is adopted, whereas the positive and negative charge differences are, respectively, denoted as red and gray clouds (for details, see Supplementary Note 6). e The dimension evolution of CDW phases from high to low temperatures in CuTe.