Quasiparticle Dispersion of the 2D Hubbard Model: From an Insulator to a Metal

On the basis of quantum Monte Carlo results the evolution of the spectral weight $A(\mathbf{k},\omega )$ of the two-dimensional Hubbard model is studied from insulating to metallic behavior. As observed in recent photoemission experiments for cuprates, the electronic excitations display essentially doping-independent features; a quasiparticlelike dispersive narrow band of width of the order of the exchange interaction $J$ and a broad valence- and conduction-band background. The continuous evolution is traced back to one and the same many-body origin: the doping-dependent antiferromagnetic spin-spin correlation.