CONTINUOUS EVOLUTION OF THE 2D HUBBARD-MODEL FROM AN INSULATOR TO A METAL

We present Quantum-Monte-Carlo results for the momentum and frequency dependent spectral weight A(k, omega) showing the evolution from insul ating to metallic behavior in the two-dimensional Hubbard model. As ob served in recent photoemission experiments for cuprates, in both undop ed and doped cases the electronic excitations display two rather simil ar general features, i.e. a quasiparticle (QP)-like dispersive band of small width of the order of the exchange interaction J and a broad va lence- and conduction-band background. Arguments for one and the same many-body physics namely the continuous reduction of the spin-spin cor relation length and related changes in the QP-spin correlations behind the continuous evolution to the metallic QP dispersion are given.