Estimate of Hubbard U for C60 by use of optical absorption.

摘要: We consider the optical absorption of ${\mathrm{C}}_{60}$ within a simple tight-binding model. To obtain reasonable agreement with experiment sizable Hubbard U must be included. estimate to in range from one-half full ``bandwidth'' where bandwidth is roughly 13 eV. In our picture two lowest-energy large-absorption peaks are due single-particle transitions: ${\mathit{H}}_{\mathit{u}}$ goes ${\mathit{T}}_{1\mathit{g}}$ and ${\mathit{H}}_{\mathit{g}}$ ${\mathit{T}}_{1\mathit{u}}$, respectively. The weak 3.0 1.9 eV attributed dipole-forbidden transition: ${\mathit{T}}_{1\mathit{u}}$ ``split'' by electron-electron repulsion.