Raman scattering study of phonon and spin modes in (TMTSF)(2)PF6

We have studied polarized Raman spectra of bis-(tetramethyltetraselenafulva lene)hexafluorophosphate ((TMTSF)(2)PF6) single crystals in the wide spectr al and temperature range using different laser energies. We observed and as signed 23 Raman active modes. The carbon C=C in-phase and out-of-phase stre tching modes at 1464 and 1602 cm(-1) show strong electron molecular vibrati on (EMV) coupling. The mode at about 1565 cm(-1) is temperature independent below 50 K due to the methyl group motion freezing. For (TMTSF)(2)PF6 in t he spin density wave (SDW) phase for a temperature induced dimensionality 1 D (quarter-filled dimerized linear chain with correlated electrons) the spi n gapless magnon spectra have been calculated. No evidence of spin-lattice coupling or spin-related modes is found in the Raman spectra in the spin de nsity wave (SDW) phase. (C) 2001 Elsevier Science B.V All rights reserved.