We study the effect of long-range Coulomb interaction on the phason in spin-density waves (SDW's) within mean-field theory. In the longitudinal limit and in the absence of SDW pinning, the phason is completely absorbed by the plasmon due to the Anderson-Higgs mechanism. In the presence of SDW pinning or when the wave vector q is tilted from the chain direction, though the plasmon still almost exhausts the optical sum rule, another optical mode appears at ω<2Δ(T), with small optical weight. This low-frequency mode below the SDW gap may be accessible to electron-energy-loss spectroscopy.
ASJC Scopus subject areas
- Condensed Matter Physics