Drude Weight, Optical Conductivity of Two-Dimensional Hubbard Model at Half Filling

We study the Drude weight D and optical conductivity of the two-dimensional (2D) Hubbard model athalf filling with staggered magnetic flux (SMF).When SMF being introduced,the hopping integrals are modulated bythe magnetic flux.The optical sum rule,which is related to the mean kinetic energy of band electrons,is evaluatedfor this 2D Hubbard Hamiltonian.Our present result gives the dependence of the kinetic energy,D and the opticalconductivity on SMF and U.At half filling D vanishes exponentially with system size.We also find in the frequencydependence of the optical conductivity,there is 6-function peak at ω≈2|m|U and the incoherent excitations begin topresent themselves extended to a higher energy region.