Spin mode, electrical resistivity, and thermal conductivity for the two-dimensional Hubbard model

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Abstract
The spin and electronic spectra of the two-dimensional Hubbard model doped away from half-filling (n≃0.9) are calculated in a conserving fluctuation-exchange approximation for coupling U/t up to 7 and temperature down to 30 K. We find neither a spin-density wave nor a superconducting instability. The energy of the overdamped collective spin mode decreases as T decreases and U/t increases. The Wiedemann-Franz ratio of the thermal and electrical conductivities becomes smaller than the Sommerfeld value. We make comparison with experimental data on cuprates.