Superconductivity and Pairing Fluctuations in the Half-Filled   Two-Dimensional Hubbard Model
  The two-dimensional Hubbard model exhibits superconductivity with d-wave symmetry even at half-filling in the presence of next-nearest neighbor hopping. Using plaquette cluster dynamical mean-field theory with a continuous-time quantum Monte Carlo impurity solver, we reveal the non-Fermi liquid character of the metallic phase in proximity to the superconducting state. Specifically, the low-frequency scattering rate for momenta near (\pi, 0) varies non-monotonously at low temperatures, and the dc conductivity is T-linear at elevated temperatures with an upturn upon cooling. Evidence is provided that pairing fluctuations dominate the normal-conducting state even considerably above the superconducting transition temperature. 
Michael Sentef, Philipp Werner, Emanuel Gull, Arno P. Kampf
cond-mat.str-el cond-mat.supr-con physics.comp-ph