Optical Conductivity of Heavy-Electron Liquids in the Mott-Transition Region

Abstract

The optical conductivity of the Hubbard model with strong electron correlation is examined in less-than and almost half-filled cases by assuming the formation of the Gutzwiller heavy-electron band (HEB) at the top of the lower Hubbard band (LHB), which is predicted by recent theories. The optical conductivity is the superposition of the Drude contribution within the HEB and excitations among the LHB, the HEB, and the upper Hubbard band (UHB). Their intensities are approximately proportional to 1- n except the excitations from the LHB to the UHB, n being the average number of electrons per unit cell. It is argued that the excitations from the LHB to the HEB are responsible for the anomalous spectra at mid-infrared frequencies of the optical conductivity and the Raman scattering of the high-temperature cuprate-oxide superconductors.