Extended Data Figure 6: Changes in the density of states in the CuO₂ plane and the Cu–O chains.

These are obtained from a projection of the density of states onto the copper muffin-tin spheres. a, b, In the light-induced state, the density of states of the O-deficient chain lowers in energy (a), whereas the opposite effect is observed for the Cu in the plane below (b). This corresponds to charge transfer from the planes to the chains. c, d, The density of states of the filled chain Cu is not strongly affected (c). The bands of the planar Cu atoms narrow, which leads to an increase in the density of states near the Fermi level both at sites with filled (d) and empty chains (b). The effect is already visible for a amplitude of 0.3 Å√u (blue) but becomes more prominent for larger displacements of 0.8 Å√u (purple) and 1.2 Å√u (green).