Density-matrix renormalization group study of triangular and square Hubbard models

We perform large-scale density-matrix renormalization group calculations for two-dimensional Hubbard models with a triangular lattice and a square lattice. In the triangular Hubbard model, we determined a boundary between metal and insulator and a boundary between spin-liquid and antiferromagnetic phases. The presence of spin-liquid phase is confirmed by spin-spin correlation function. In the square Hubbard model, we introduce a second-neighbor hopping interaction and calculate the dynamical spin correlation function to clarify the doping dependence of magnon excitations. We find a shift of a peak position toward higher energy in the electron-doped side, being consistent with recent resonant-inelastic x-ray scattering.