Sliding spin-density wave in (TMTSF)2PF6 studied with narrow-band noise -: art. no. 214201

We report narrow-band noise (NBN) due to sliding motions of the spin-density wave (SDW) condensate at 2.0 K in three samples of (TMTSF)(2)PF6 and the magnetic-field effects. Typical NBN spectra coming from the saw-toothed-wave current oscillations are clearly observed. The periodic peaks due to the 4k(F)-charge-density wave (CDW) collective excitation are found, together with the SDW moving with a faster velocity, revealing that the sliding mode of the SDW is coupled with 4k(F)-CDW fluctuations. Observation of the interference peaks gives evidence of spatially nonuniform dc current carried by the deformable SDW in domains. At large currents the NBN spectrum drastically changes with increasing current and depends on applied magnetic field, suggesting a dynamical phase transition from the plastic-flow phase to the moving-solid phase. In the moving-solid phase the frequencies of the periodic peaks decrease with increasing current because the spatial coherency grows rapidly. The current oscillations in this phase are interpreted in terms of the coexistence of the 2k(F)-CDW collective excitation with the phason.