Correlation between linear resistivity and Tc in the Bechgaard salts and the pnictide superconductor Ba(Fe1-xCox)2As2

The quasi-one-dimensional organic Bechgaard salt (TMTSF)(2)PF6 displays spin-density-wave (SDW) order and superconductivity in close proximity in the temperature-pressure phase diagram. We have measured its normal-state electrical resistivity rho(a)(T) as a function of temperature and pressure, in the T -> 0 limit. At the critical pressure where SDW order disappears, rho(a)(T)proportional to T down to the lowest measured temperature (0.1 K). With increasing pressure, rho(a)(T) acquires a curvature that is well described by rho(a)(T)=rho(0)+AT+BT2, where the strength of the linear term, measured by the A coefficient, is found to scale with the superconducting transition temperature T-c. This correlation between A and T-c strongly suggests that scattering and pairing in (TMTSF)(2)PF6 have a common origin, most likely rooted in the antiferromagnetic spin fluctuations associated with SDW order. Analysis of published resistivity data on the iron-pnictide superconductor Ba(Fe1-xCox)(2)As-2 reveals a detailed similarity with (TMTSF)(2)PF6, suggesting that antiferromagnetic fluctuations play a similar role in the pnictides.