Quasi-Particles in the Strong-Coupling Limit of the 2D Hubbard Model

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Abstract
The single-particle Green's function for the strong-coupling limit of the single-band Hubbard model (t-J model) at half-filling is calculated numerically using a Lanczos algorithm. Two-dimensional systems of up to 18 sites with periodic boundary conditions are examined, and evidence is presented for a coherent quasi-particle band of width J which emerges at the low-energy edge of the incoherent spectrum. We find the quasi-particle dispersion to be consistent with εk = (J/2)[cos (kx) + cos (ky)]2, corresponding to effective next-nearest-neighbour hopping.