PHASON DYNAMICS IN CHARGE AND SPIN-DENSITY WAVES

Phason propagators in charge and spin density waves in presence of long range Coulomb interaction are studied within mean field theory. In charge density wave the longitudinal phason splits into an acoustic mode and an optical mode in the presence of Coulomb interaction. Except at low temperatures (T less-than-or-equal-to 0.2 T(c)) the acoustic mode exhausts most of the optical weight. In spin density wave there is no longitudinal acoustic mode; the phason becomes the plasmon. On the other hand in the transverse limit, the plasmon decouples completely from the phason both in charge and spin density waves.