Phase diagram for the attractive Hubbard model in two dimensions in a conserving approximation
Physical Review B - Condensed Matter and Materials Physics
We calculate the superconducting transition temperature as a function of interaction strength and density for a two-dimensional attractive Hubbard model in the fluctuation exchange approximation (FEA). Significant corrections to mean-field theory are apparent, including a maximum in Tc as a function of U and a fluctuation-broadened specific heat peak. At n = 1, competing pair fluctuations and charge-density fluctuations fail to drive Tc to zero. This failure of the FEA reflects an inadequate account of the coupling among fluctuations. Because Tc is determined from self-consistent calculations of thermodynamic potentials, the calculations are extremely sensitive to numerical errors, requiring accuracy up to 1 part in 106. We outline a procedure for systematically reducing numerical errors associated with the finite-frequency cutoff in numerical many-body calculations such as ours.
Original Publication Date
DOI of published version
Deisz, J. J.; Hess, D. W.; and Serene, J. W., "Phase diagram for the attractive Hubbard model in two dimensions in a conserving approximation" (2002). Faculty Publications. 3388.