LOWER AND UPPER HUBBARD BANDS - A SLAVE-BOSON TREATMENT

We analyze the single-particle spectral density and the optical conduc tivity of the single-band Hubbard model in the insulating Mott phase w ithin the slave-boson technique. We show that the boson fluctuations a round the saddle-point solution build up the lower and upper Hubbard b ands and give rise to the optical conductivity which describes transit ions between these incoherent bands. We find that the Brinkman-Rice me tal-insulator transition is characterized by the simultaneous vanishin g of the jump in the chemical potential, the single-particle spectral density gap, and the optical gap.