Temperature dependence of electronic states in the t-J model.

Abstract

The temperature dependence of electronic states in the t-J model is studied in the moderately doped region by use of the composite operator method. Self-energy effects are included in two-site approximation. At higher temperature, the density of states shows a two-peak structure, and the coherent peak at the Fermi level increases its intensity with decreasing temperature. The peak at the Fermi level splits into two peaks with further decreasing temperature, corresponding to the electronic excitations from spin-singlet and -triplet states of the nearest-neighbor electrons. Electronic excitations from the singlet states form a narrower band at the Fermi level. This may relate to the spin gap formation observed in high-${\mathit{T}}_{\mathit{c}}$ superconductors. \textcopyright{} 1996 The American Physical Society.