Fig. 1
Electronic structure of the gold–silica–gold nanojunctions. a Energy diagram of the nanojunction in the presence of a laser E(t). The junctions are composed of N unit cells of α-SiO2 grown along the a (E || a) or c (E || c) crystallographic directions and connected by its ends to metallic contacts. The lead’s Fermi energy μF is taken to be between the valence band (VB) and conduction band (CB). Here, Γ/ħ is the charge transfer rate between each Wannier functions at the terminal unit cells to the corresponding lead and μ α (t) the chemical potential of left (α = L) and right (α = R) contact. b Band structure of α-SiO2 computed using density functional theory (solid lines) and the generalized tight-binding model (open circles) based on maximally localized Wannier functions (MLWFs). The model consists of 27 MLWFs per unit cell that result in 18 VBs and 9 CBs. It accurately reproduces the band structure in a wide energy range and the 9 eV experimental band gap. The relevant electronic structure along the a and c-direction are highlighted. c Isosurface contours of four representative MLWFs (red for positive value and blue for negative)
