OPTICAL CONDUCTIVITY OF THE HUBBARD-MODEL AT FINITE-TEMPERATURE

The optical conductivity, sigma(omega), of the two-dimensional one-band Hubbard model is calculated at finite temperature using exact diagonalization techniques on finite clusters. The in-plane dc resistivity, rho(ab), is also evaluated. We find that at large U/t and temperature T, rho(ab) is approximately linear with temperature. We also observed that sigma(omega) displays charge excitations, a midinfrared (MIR) band, and a Drude peak. The combination of the Drude peak and the MIR oscillator strengths leads to a conductivity that decays slower than 1/omega2 at energies smaller than the insulator gap near half filling.