In this paper we show that local spin-singlet amplitude with d-wave symmetry, $<|\Delta_{ d}(0)|^{ 2}>$, can be induced by short-range spin correlations even in the absence of pairing interactions. Fluctuation theory is formulated to make connection between pseudogap temperature $T^{ *}$, pseudogap size $\Delta_{ pg}$ and $<|\Delta_{ d}(0)|^{ 2}>$. In the present scenario for the pseudogap, the normal state pseudogap is caused by the induced local spin-singlet amplitude due to short-range spin correlations, which compete in the low energy sector with superconducting correlations to make $T_{ c}$ go to zero near half-filling. Calculated $T^{ *}$ falls from a high value onto the $T_{ c}$ line and closely follows mean-field N\'{ e}el temperature $T_{ N}^{ MF}$. The calculated $\Delta_{ pg}$ is in good agreement with experimental results. We propose an experiment in which the present scenario can be critically tested.
Categories: cond-mat.str-el cond-mat.supr-con