2 HUBBARD BANDS - WEIGHT TRANSFER IN OPTICAL AND ONE-PARTICLE SPECTRA

We identify local kinetic-energy contributions which are responsible f or the rapid weight transfer from the high- to the low-energy scale ob served upon doping in strongly correlated materials. Using strong-coup ling perturbation theory for the Hubbard model we derive expressions f or the weights of the upper and lower Hubbard bands separately and eva luate them explicitly in one dimension. The optical conductivity is fo und to be a direct probe of the local spin order.