Figure 1

Crystal structure and static band properties of K${}_{0.3}$MoO${}_3$. (a) Linear chains of MoO${}_6$ octahedra form slabs, which make up the $b$-$d$ cleavage plane. (b) Upper panel: static ARPES intensity map at $t$ $=$ −50 fs and 20 K as a function of binding energy and momentum. To bring out the underlying band structure, we also plot ${\partial }^{2}I/\partial E^2$ (lower panel). The dashed blue and red lines locate the antibonding ($A$1 and $A$2) and bonding ($B$1 and $B$2) bands. Vertical arrows mark the different Fermi wave vectors. The photoelectron momentum is measured along the cut direction indicated on the zone map shown in the inset. (c) Individual EDCs used to produce the intensity map. EDCs at the Fermi momenta are highlighted and are labeled.Reuse & Permissions

Figure 2

Response to impulsive excitation by a femtosecond laser pulse. (a) Photoemission intensity maps at $-$50 and 250 fs, shown on the same color scale. The arrows mark the centers of increased intensity above $E_F$. (b) Photoinduced changes in the EDCs at $k_F^{\left(B1\right)}$ and $k_F^{\left(A2\right)}$ with intensity transferred from the valence bands to $E_F$ as the CDW phase melts in response to the excitation pulse.Reuse & Permissions

Figure 3

Time evolution of the electronic structure near the gap edge for each Fermi wave vector as labeled. Symbols: intensity near $E_F$, integrated from $-$50 to $+$100 meV. Solid lines: fits to the integrated intensity. The model contains an exponential decay plus a sine function with frequencies of 1.7 THz (a), 0.8 THz (b), or both (c and d).Reuse & Permissions

Figure 4

Collective excitations of the CDW state. (a) Free energy of the ground state (blue) and the excited state (red) as a function of amplitude |Δ| and phase Φ of the complex order parameter. As the minimum of the free energy in the excited state is located at a different |Δ|'s compared to the ground state, amplitude oscillations are excited (yellow arrows). (b) Idealized dispersion and snapshots of the charge density of an amplitude mode (red) and phase mode (blue). Arrows indicate a parametric generation process from ${\omega }_A\left(0\right)$ to ${\omega }_P\left(\pm q_P\right)={\omega }_A\left(0\right)/2$. (c) Coherent phase-mode oscillations obtained by solving the coupled differential equations given in the text for different ratios of ${\omega }_A/{\omega }_P$. (d) Dispersion (red curves) and Fermi-surface nesting (green arrow) in the presence of a time-dependent phase.Reuse & Permissions