Fig. 1: Fluence-dependence of photoinduced phase transitions in VO2.
From: Photoinduced hidden monoclinic metallic phase of VO2 driven by local nucleation
a The atomic structure of the 2 × 2 × 2 supercell for the insulating monoclinic (M1) phase. Here, V and O atoms are labeled by purple and orange balls, respectively, and the dashed gray parallelepiped represents the unit cell. The Peierls lattice distortion along the a-axis causes V-V dimerization with the bonds of the V-V dimers (with a bond length dS) and the bonds of long counterparts (with a bond length dL) represented by purple lines and gray lines, respectively. The time evolution of the real-space distribution of photoexcited holes on the (010) plane for M1-phase VO2 following (b) a strong photoexcitation and (c) a weak photoexcitation, respectively. For comparison, the initial positions of the V atoms before photoexcitation are indicated by white balls, and the photoinduced atomic driving forces on V atoms are marked by white arrows with their length indicating the relative force strength. d The corresponding 2 × 2 × 4 supercell of the metallic rutile (R) phase, in which all V-V bonds (purple lines) along the a-axis are equally distributed at dR. The blue shading indicates a 3D isosurface of the partial charge density of the bands around the Fermi level as marked in (g). e The 2 × 2 × 2 supercell structure of the metal monoclinic (MM) phase with a 3D isosurface of the partial charge density of an isolated band around the Fermi level marked in (h). The V atoms in a chain with larger displacements are labeled by Arabic numerals 1–4. The first-principles calculations predicted unfolded band structures of the M1 phase (f), the R phase (g), and the MM phase (h).
