Pseudogap Formation in an Electronic System with d-wave Attraction at Low-density

On the basis of an electronic model with separable attractive interaction, the precursors at high temperature and strong coupling of the d-wave superconducting state are investigated in the one-particle spectral function $A({\bf k},\omega)$ and the total density of states $\rho(\omega)$, with the use of the self-consistent $t$-matrix approximation. In the low-density region, it is found that a gap-like structure at the Fermi level appears in $A({\bf k},\omega)$ and $\rho(\omega)$ above the superconducting transition temperature. It is shown that the pseudogap energy scale is determined by the binding energy of the Cooper-pair.