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

Abstract

We have studied polarized Raman spectra of (TMTSF)2PF6 single crystals in the wide spectral and temperature range using different laser energies. We observed and assigned 23 Raman active modes. The carbon C=C in-phase and out-of-phase stretching modes at 1464 cm-1 and 1602 cm-1 show strong electron-molecular-vibration coupling. The mode at about 1565 cm-1 is temperature independent below 50 K due to the methyl group motion freezing. For (TMTSF)2PF6 in the spin density wave phase for a temperature induced dimensionality 1D (quarter filled dimerized linear chain with correlated electrons) the spin 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 density wave phase.