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

The response functions, χ, 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, tperpendicular, enhances χ of SDW having the dependence on temperature with the power-law even below the crossover temperature Tx∼tperpendicular. Further, χ of the d-wave singlet superconductivity (dSS) is enhanced rapidly below Tx by tperpendicular, while there is no dominant behavior for dSS in the one-dimensional case (tperpendicular=0). The results suggest that tperpendicular (or the pressure) rises the transition temperature of dSS even after the SDW is destroyed by the pressure