FIG. 6. Color online Spectral weight for four representative densities for the t-t model see Fig. 5 . The progression from top to bottom is from high electron concentration to low electron concentration. Note the qualitative change from negative slope lowersuperconducting vs normal-state difference to positive slope higher-superconducting vs normal-state difference as the electron concentration changes such that the chemical potential sweeps through the van Hove singularity.
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