Role of fluctuations in density wave and superconductivity of quasi-one-dimensional conductors

The response functions, chi, for the spin density wave (SDW) and the superconductivity in the quasi-one-dimensional electron systems at quarter-filling are calculated by the newly developed N-chain renormalization group method. It is shown that the interchain hopping, t(perpendicular to), enhances chi of SDW having the dependence on temperature with the power-law even below the crossover temperature T-x similar to t(perpendicular to). Further, chi of the d-wave singlet superconductivity (dSS) is enhanced rapidly below T-x by t(perpendicular to), while there is no dominant behavior for dSS in the one-dimensional case (t(perpendicular to) = 0). The results suggest that t(perpendicular to) (or the pressure) rises the transition temperature of dSS even after the SDW is destroyed by the pressure. (c) 2006 Published by Elsevier B.V.