13C NMR investigation of the linear and nonlinear dynamics of the spin-density wave of (TMTSF)2PF6

The interpretation of our recent measurements of the temperature dependence of the NMR spinlattice relaxation rate in the spin-density wave (SDW) state in (TMTSF)2PF6, as well as of our combined conduction noise and NMR spectra measurements in the sliding SDW state is discussed in relation with the prominent features of the electric response. Our measurements suggest that the phason effective mass is equal to the band mass, and show that the condensate density is not strongly reduced, as has been proposed. Consequences on the dynamics of the phason, and especially the so-called pinned mode resonance, are discussed