Fig. 5: Ab-initio electronic band structure and DFT-DMFT spectral function in K₃C₆₀.

a DFT electronic band structure of the 1tu bands adapted from ref. ⁶¹, with red color corresponding to the upper unoccupied 1tu band and blue color to the two occupied lower 1tu bands. b Electron spectral functions using DFT and DMFT adapted from ref. ³⁹. Orange-shaded figure corresponds to the DFT spectral function while the DMFT spectral function, which includes renormalization due to electron-electron interaction, is given by the purple curve. Using the above data, we take the gap between occupied and unoccupied 1tu bands to be the distance between the two peaks in the density of states, ΔE_DFT for the DFT spectral function and ΔE_DMFT for the DMFT spectral function. We see that interaction effects can significantly renormalize the band structure.