We investigate temperature dependence of spin correlations in the one-dimensional Hubbard model at or close to half filling by the quantum Monte Carlo method. The numerical data are analyzed by introducing a crossover generated from an interplay of the intrinsic correlation length and the thermal correlation length. It provides a unified picture of the spin correlation of the metallic phase near the Mott insulator at finite temperatures. Our results show that the crossover, not taken account by the conventional renormalization group and the conformai field theory, becomes more and more important to understand the spin correlation near the Mott transition point.
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