Magnetic Properties and Superconductivity in the Two-Dimensional Repulsive Hubbard Model

A new method for estimating the parameter ensuring the fulfillment of the Mermin-Wagner theorem in the strong coupling diagram technique (SCDT) for the two-dimensional Hubbard model is suggested. With the precise parameter value, calculated magnetic quantities are in good agreement with the results of numeric and optical-lattice experiments. Obtained spin and charge vertices are used for investigating superconductivity in the t-U and t-t'-t ''-U Hubbard models in the regime of strong correlations. We found no superconducting transition in the t-U model. In the t-t'-t ''-U model, the transition occurs for the singlet d(x2 - y2) pairing at T-c approximate to 0.016t. The difference between the two models is in the renormalized hopping describing electron motion in SCDT. In the t-U model, it vanishes for momenta (pi, 0), (0, pi) of extrema of the d-wave order parameter, while the hopping is finite in the t-t'-t ''-U model. In the one-band model, there are optimal values of t' and t '' ensuring the highest T-c.

Automated summary

A new method is suggested to estimate parameters for the two-dimensional Hubbard model to ensure the fulfillment of the Mermin-Wagner theorem in the strong coupling diagram technique (SCDT). The calculated magnetic quantities are in good agreement with experiment results, and the obtained spin and charge vertices are used to investigate superconductivity under strong correlations. While no superconducting transition is found in the t-U model, a transition occurs in the t-t'-t ''-U model at approximately T-c=0.016t. The difference between the two models lies in the renormalized hopping parameters describing electron motion in SCDT.