Numerically exact diagonatization study of Drude weight and chemical potential in two-dimensional Hubbard model

The doping dependence of the Drude weight as well as the chemical potential in the strong-coupling limit of the two-dimensional Hubbard model is examined by applying the exact diagonalization technique to a 20×20 cluster. We impose twisted boundary conditions (BC) instead of standard periodic BC and perform averaging procedure over the twisted BC to reduce the finite-size effect. We find that the chemical potential near half filling is proportional to the square of the carrier concentration, while the Drude weight is approximately linear in the concentration. We discuss implications of the results comparing with other theoretical studies.